JPH0613334A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] MOVPE for III-V group compound semiconductor layers
It is an object of the present invention to provide a method for manufacturing a semiconductor device including a step of crystal growth by (organic metal vapor phase epitaxy), in which Mg is used as a p-type dopant, and a doping delay is reduced. A method of manufacturing a semiconductor device, comprising the step of crystallizing a III-V compound semiconductor layer by MOVPE, wherein the organic compound of Mg is used as a p-type impurity in MOVPE crystal growth of a p-type III-V compound semiconductor layer. Using a mixed gas of a metal compound and an organometallic compound of Al, including a step of growing a Mg-doped p-type layer containing Al as a Group III element in the range of about 0.02 to about 0.1 in the vicinity of the interface at the initial growth stage. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a III-V compound semiconductor layer formed by MOVPE.
The present invention relates to a method for manufacturing a semiconductor device including a step of crystal growth by (organic metal vapor phase epitaxy).

A light source for reading and writing optical discs,
There is an increasing demand for visible light semiconductor lasers as light sources for POS systems, light sources for printers, and the like. As such a visible light semiconductor laser, AlGaI using GaAs as a substrate is used.
An nP semiconductor laser or the like is used.

[0003]

2. Description of the Related Art GaAs substrate and GaInP or AlG
An AlGaInP-based visible light semiconductor laser can be constructed by using an aInP active layer and sandwiching both sides of the active layer with an AlGaInP clad layer.

FIG. 5A shows a conventional AlGaInP /
An example of the structure of a (Al) GaInP visible light semiconductor laser is shown. An n-type GaAs buffer layer 62 is grown on an n ⁺ -type GaAs substrate 61, and then an n-type AlGaInP clad layer 63 is grown to form an n-type region. In addition,
As the n-type impurity, a group IV element Si or a group VI element S
Commonly used n-type impurities such as e and S can be used.

Undoped GaInP is formed on the n-type region.
Alternatively, an AlGaInP active layer 64 is formed, and a p-type AlGaInP clad layer 65 and a p-type GaInP are formed on the active layer 64.
The intermediate layer 67a is formed. Then, a stripe mask of SiO ₂ is formed on the surface. Mesa etching is performed using the SiO ₂ mask as an etching mask to remove the middle portion of the p-type cladding layer 65.

Using the SiO ₂ mask used for the mesa etching also as a growth mask, the n-type GaAs current blocking layer 66 is grown to fill the side surface of the mesa. This GaAs
The current blocking layer 66 provides optical confinement in the lateral direction with respect to the active layer 64 and current confinement for hole current.
Then, the surface is further covered with a p-type GaAs contact layer 68a.
And a semiconductor laser structure is formed.

The n-side electrode 6 is formed on the lower surface of the n ⁺ type GaAs substrate 61 and the upper surface of the p type GaAs contact layer 68a.
9, p-side electrode 70 is formed. In the semiconductor laser having the structure shown in FIG. 5A, it is desired that the resistivity of the p-type clad layer 65 be as low as possible to suppress heat generation therein and to effectively confine the injected carriers. For this purpose, it is desired to increase the doping concentration of the p-type cladding layer 65 and the p-type intermediate layer 67a as much as possible.

FIG. 5B shows another structure of the AlGaInP / GaInP visible light semiconductor laser. A stripe-shaped mesa structure is formed on the surface of the Zn-doped p-type GaAs substrate 111.

Se-doped n-type GaA covering the side surface of the mesa
The s current blocking layer 112 is formed, and a reduced mesa structure is formed on the surface thereof. The current blocking layer 112 forms a potential barrier for holes transported from the p-type substrate 111 and concentrates the hole current on the top of the mesa.

On such a composite mesa structure, a Zn-doped p-type GaAs buffer layer 113 and a Zn-doped AlG are formed.
The aInP clad layer 115 is formed. here,
The intermediate layer 114 includes the buffer layer 113 and the cladding layer 115.
It has a band gap intermediate between and.

On these p-type regions, undoped G
An active layer 116 made of aInP is formed, and an n-type region is stacked thereon. First, Se-doped n-type Al
A GaInP clad layer 117 is formed, and Se is formed thereon.
Doped GaInP intermediate layer 118, Se-doped n-type G
The aAs contact layer 119 is formed. Here, the intermediate layer 118 has a band gap intermediate between the clad layer 117 and the contact layer 119.

These laminated structures are epitaxially grown on the mesa structure and have a curved surface following the mesa structure. With this structure, an optical waveguide is formed on the top of the mesa. Since the position of the optical waveguide is self-aligned with the mesa structure, this structure is self-aligned bent waveguide (self-aligned bent wavegu
ide laser).

The intermediate layer 114 has a band gap intermediate between the buffer layer 113 and the cladding layer 115, but potential barriers called spikes are generated at both ends of the intermediate layer 114 due to the heterojunction.

In order to reduce the current blocking due to the potential barrier, the buffer layer 113, the intermediate layer 114, and the cladding layer 115 are uniformly doped with high-concentration p-type impurities or the band structure is changed continuously. It is desirable to adopt a simple graded structure. This also applies to the structure of FIG. 5A.

The AlGaInP-based material is generally crystal-grown by using metal organic vapor phase epitaxy (MOVPE). p
Zn is usually used as the type dopant, and dimethyl zinc (DMZn, (CH ₃ ) ₂ Zn) is used as the source material thereof.
Or diethyl zinc (DEZn, (C ₂ H ₅ ) ₂ Zn)
Is used.

However, Zn has a high vapor pressure, and re-desorption of Zn from the crystal surface is remarkable, so that high-concentration doping (5 ×
10 ¹⁷ cm ⁻³ or more) is difficult. Zn is AlGaIn
Large diffusion in P-type crystals. When Zn is doped into an AlGaInP-based crystal, a reaction byproduct is generated with In or P, which becomes a nucleus of crystal defects.

Thus, Zn as a p-type dopant
Has some problems. Therefore, Mg is expected as a dopant replacing Zn. Mg can be highly doped (about 2 × 10 ¹⁸ cm ⁻³ ). Mg has small diffusion in AlGaInP-based crystals. Mg is Al
It does not form a reaction by-product with the GaInP-based host material.

[0018]

Thus, Mg as a p-type dopant has many advantages. However, AlGaI
For Mg as a p-type dopant in an nP-based material,
There is a problem of doping delay. Even if Mg is doped during crystal growth, the desired amount of M is initially obtained.
g is not doped. That is, it takes time from the start of supplying Mg until the Mg is actually taken into the crystal.

This phenomenon of doping delay is relatively small in AlGaInP-based materials containing Al, but it appears remarkably in GaInP, GaAs, etc. not containing Al, which is a serious problem. It is known that the doping delay can be reduced by increasing the amount of Mg raw material, but it is difficult to control in a region corresponding to a practically important carrier concentration, which is a serious problem.

Nishikawa et al.
The doping delay greatly changes depending on the growth temperature and whether the host material is InAlP or InGaP. This doping delay is a model in which doping does not start until a certain amount of Mg is accumulated on the solid phase surface. Can be explained by. (Extended Abs
tracts of the 22nd, 1990 International Conference o
n Solid State Devices and Materials, Sendai, 1990, p
p.509-512). Hatano et al. proposed to use an adduct of trimethylaluminum and dimethylmagnesium to achieve Mg doping without doping delay. (Appl.Phys. Lett., Vol.5
8, No. 14, 1991, pp. 1488-1490).

The phenomenon of doping delay in Mg doping will be described with reference to FIG. 5C. FIG. 5C shows a case where a Mg-doped GaAs epitaxial film is grown on a Zn-doped GaAs substrate. The horizontal axis shows the depth from the surface, and the vertical axis shows the concentration of the dopant.

In the GaAs epitaxial film, although Mg was doped from the initial growth stage,
The concentration is extremely low at the beginning of growth and gradually rises as the growth progresses to some extent.

At the initial stage of the growth of the GaAs epitaxial film, some Zn enters from the Zn-doped GaAs substrate due to diffusion, so that it becomes p-type. However, after the Zn concentration drops, until the Mg concentration rises. The region has a very low impurity concentration and becomes a high resistance region.

M having such a doping delay phenomenon
A more specific problem when g is used as a p-type dopant will be described with reference to FIG. 5D. In FIG. 5D, p
^A p-type GaAs buffer layer 72 is grown on a ⁺ -type GaAs substrate 71, and a p-type GaInP intermediate layer 73, p is formed thereon.
A type AlGaInP clad layer 74 is grown to form a p-type region. An undoped GaInP layer 75 is grown on the p-type region as an active layer, and n-type AlGaIn is formed on the active layer.
The P-clad layer 76 and the n-type GaAs contact layer 77 are grown to form an n-type region.

Here, the GaAs buffer layer 72, GaI
Mg is doped as a p-type dopant for the nP intermediate layer 73 and the AlGaInP cladding layer 74. Then, the GaAs buffer layer 72 and the GaInP intermediate layer 7
In No. 3, Mg may not be doped easily and the desired p-type may not be obtained. In some cases, these regions become n-type. As described above, unless desired Mg is doped, a current does not flow in the diode structure that should have been manufactured, or IV characteristics are deteriorated.

An object of the present invention is to provide a method for manufacturing a semiconductor device which uses Mg as a p-type dopant and which reduces the doping delay.

[0027]

A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device including a step of crystal-growing a III-V group compound semiconductor layer by MOVPE, which is a p-type group III-V group. In MOVPE crystal growth of the compound semiconductor layer, a mixed gas of an organometallic compound of Mg and an organometallic compound of Al is used as a p-type impurity, and Al is added as a group III element in the vicinity of the interface at the initial stage of growth of about 0.02 to about 0 Including the step of growing a Mg-doped p-type layer containing 0.1 or less.

[0028]

When the organometallic compound of Mg and the organometallic compound of Al are mixed and used as a dopant, the doping delay phenomenon is reduced. Therefore, various problems due to the doping delay phenomenon are reduced.

[0029]

1A and 1B show the basic concept of the present invention. FIG. 1A schematically shows a method for manufacturing a semiconductor device,
FIG. 1B shows the structure of a p-type III-V group compound semiconductor layer in a semiconductor device.

As shown in FIG. 1A, when the p-type III-V group compound semiconductor layer 7 is grown, the organometallic compound 1 of Mg is used.
Is used as the p-type dopant, and at the same time, the organometallic compound 2 of Al, which is not necessary for the composition of the growth layer, is mixed with the organometallic compound 1 of Mg as shown in the mixing section 4. However, in order to prevent the mixed Al from substantially affecting the energy gap and the refractive index of the growth layer, the added amount of Al is set to 0.1 or less as a composition.

A gas of another raw material 3 is added to this mixed gas as shown in the mixing section 5, and the obtained source gas is used to perform CVD growth on the underlying crystal 6 to perform p-type III-V group compound semiconductor. Grow layer 7.

FIG. 1B shows an example of the structure of a semiconductor device manufactured by the manufacturing method shown in FIG. 1A. At least on the underlayer 9 having an i-type or n-type region on the surface, Mg
III-V compound semiconductor layer 7 doped with Al and Al
a and 7b are arranged, and the p-side electrode or the p-type substrate 8 is arranged thereon. Group III-V compound semiconductor layer 7
a and 7b are the p-side electrode or the p-type substrate 8 and the i-type or n
The base layers 9 of the mold are connected.

The crystal growth includes not only the case of going from the lower side to the upper side of FIG. 1B but also the case of going from the upper side to the lower side. The Mg doping delay is said to be due to the organometallic compound of Mg adhering to the quartz pipe, the quartz reaction tube, or the like.

The reason why the doping delay phenomenon is reduced by adding Al together with Mg is not clear, but M
It is considered that when the organometallic compound of g and the organometallic compound of Al are mixed, the properties of the organometallic compound of Mg are changed, and the rate of adhesion to the pipes, reaction tubes, etc. in the middle is reduced.

By adding Al, Al is mixed into the growing layer to change the composition of the growing layer.
The amount of 1 is not so large, and the degree of changing the characteristics of the semiconductor device is weak.

FIG. 2 schematically shows a CVD crystal growth system for carrying out the method for manufacturing a semiconductor device according to the embodiment of the present invention. In the quartz reaction tube 11, the susceptor 12
And a base substrate 13 for crystal growth is arranged on the susceptor 12.

A raw material gas for crystal growth is supplied to the reaction tube 11 from a gas switching manifold 15 for gas switching through a pipe 21 for supplying a source gas. The gas switching manifold 15 has a supply pipe 21 and a disposal pipe 22, and pipes 23, 24 from each raw material gas.
Is connected to the pipes 22 and 21 by the interlocking switching valve 18 including the switching valves 16 and 17.

For example, when one of the valves 16a and 17a of the interlocking switching valve 18a is open, the other is closed. In the illustrated state, the valves 17a, 17b, 1
7i shows a closed state.

The carrier gas such as H ₂ and N ₂ from the carrier gas pipe 27 is passed through the mass flow controller 31 to cyclopentadienyl magnesium (Cp ₂ Mg) 3
3 is supplied to the container 32 containing 3 and is supplied to the pressure control valve 34 in a state of containing the gas of Cp ₂ Mg.
In addition, trimethylamine alane (CH
₃ ) ₃ NAlH ₃ , dimethylamine alane (CH ₃ ) ₂
An amine-based material such as C ₂ H ₅ NAlH ₃ can also be used. Similarly, amine-based Mg can also be used.

The carrier gas from the carrier gas pipe 27 is also directly supplied to the pressure control valve 34 via the mass flow controller 35. A pressure gauge 36 is connected in the middle of a pipe from the mass flow controller 35 to the pressure control valve 34, and the measured pressure is fed back to the pressure control valve 34 via a control line 38 to maintain a constant pressure. The dopant gas supplied from the pressure control valve 34 enters the gas switching manifold 15 via the pipe 23 and is supplied to the reaction tube 11 via the valve 17b or is discarded via the valve 16b.

As cyclopentadienyl magnesium, biscyclopentadienyl magnesium (C
₅ H ₅ ) ₂ Mg or bismethylcyclopentadienyl magnesium (CH ₃ C ₅ H ₄ ) ₂ Mg is preferably used.

The carrier gas from the carrier gas pipe 28 contains a liquid 43 of trimethylaluminum (CH ₃ ) ₃ Al (TMA) or triethylaluminum (C ₂ H ₅ ) ₃ Al (TEA) via the mass flow controller 41. After being introduced into the container 42 and subjected to bubbling, it is supplied to the pipe 24 via the pressure control valve 44.

The carrier gas from the carrier gas pipe 28 is also directly supplied to the pressure control valve 44 via the mass flow controller 45. A pressure gauge 46 is connected in the middle of the pipe from the mass flow controller 45 to the pressure control valve 44, and the measured value of the pressure gauge is the control line 4.
It is fed back to the pressure control valve 44 via 8.

In this way, the pressure is kept constant on the upstream side of the pressure control valve 44. The pipe 24 connected to the pressure control valve 44 is connected to the reaction tube 1 via the valve 17a.
1 or to the disposal side via the valve 16a.

The pipe 101 is H₂Or N₂The key
Carrier gas is supplied to the mass flow controller 108.
A carrier gas is supplied to the pipe 109 via. Piping 1
02 is 10 to 20% H stored in the cylinder 103₂Rare
Buddha's arsine (AsH₃) Is pressure reducing valve 104, valve
The mass flow controller 10 is supplied via 105.
It is connected to the pipe 109 via 7. In addition, similar structure
Phosphine (PH ₃) H₂Dilution gas is also supplied
It

In the entire reaction system, trimethylindium (TMIn) is used as the In source and T is used as the Ga source.
MGa or TEGa, AsH ₃ , P as As source
PH ₃ is connected to the gas switching manifold 15 as a source. The carrier gas is H ₂ during crystal growth, and N ₂ gas is used for purging before or after growth.

In a normal MOVPE, the inside of the reaction tube 11 is kept under a reduced pressure atmosphere of the order of 10 Torr, and the upstream side of the pressure control valve is kept at about atmospheric pressure. As Cp ₂ Mg used as a dopant and TMA or TEA used as an additive, semiconductor grade high purity ones are used in order not to impair the characteristics of the growth layer.

The source gas of the III-V group compound semiconductor to be grown is supplied to the pipe 21 from another supply line via the gas switching manifold 15. Mg
When growing a p-type III-V group compound semiconductor layer doped with Mg, a predetermined amount of Al source gas is always supplied together with the Mg source gas.

FIG. 3 schematically shows another CVD crystal growth system for carrying out the method of manufacturing a semiconductor device according to an embodiment of the present invention. The reaction tube 11, the susceptor 12, the base substrate 13, the gas switching manifold 15, the supply pipe 21, and the disposal pipe 22 are the same as those shown in FIG.

In this structure, the organometallic compound of Mg, which is a p-type dopant, is supplied to the valves 16a and 17a of the gas switching manifold 15 from the pipe 26 in a state of being mixed with the organometallic compound of Al.

Carrier gas such as H ₂ and N ₂ from the carrier gas pipe 29 is introduced into the container 52 accommodating the organometallic compound 53 of Al such as TMA and TEA through the mass flow controller 51 and bubbled. It is supplied to the pressure control valve 57.

[0052] The carrier gas is supplied to the vessel 55 containing the organometallic compound 54 Mg of Cp ₂ Mg or the like through a mass flow controller 56a, the pressure in a state of a mixture of vapors of Cp ₂ Mg control valve 57 Is supplied to.

Further, the carrier gas is directly supplied to the pressure control valve 57 via the mass flow controller 56. From the mass flow controller 56 to the pressure control valve 5
A pressure gauge 58 is connected in the middle of the pipe reaching 7 and a control signal based on the measured pressure is fed back to a pressure control valve 57 via a control line 59, so that the pressure control valve 57
To control.

As described above, in this structure, the organometallic compound of Mg and the organometallic compound of Al are mixed in a relatively high pressure state on the upstream side of the pressure control valve 57, and the low pressure side pipe from the pressure control valve 57 is mixed. 26. Since the organometallic compound of Mg and the organometallic compound of Al are mixed at a relatively high pressure, a more homogeneous mixed gas can be supplied.

It was investigated whether trimethylaluminum and biscyclopentadienylmagnesium react with each other at room temperature under normal pressure to purify other compounds.
Put Cp ₂ Mg and TMA in the flask, mix, and 50 ℃
The mixture was heated and stirred for 3 hours.

The pressure in the reaction system was reduced to 0.5 Torr, unreacted TMA was extracted, and the remaining powder was heated to 50 to 90 ° C. /
Sublimated at 0.5 Torr. Elemental analysis was performed on the first few grams and the last few grams.

From the results, it was estimated that both samples remained Cp ₂ Mg. Therefore, it can be presumed that no reaction has occurred between trimethylaluminum and biscyclopentadienylmagnesium in the above-mentioned reaction furnace.

FIG. 4 shows an example of the structure of a semiconductor device produced by using the CVD crystal growth system shown in FIG. 2 or 3. In the visible light semiconductor laser shown in FIG. 4, the n-type GaAs buffer layer 6 is formed on the n ⁺ -type GaAs substrate 61.
2. An n-type AlGaInP clad layer 63 is arranged, and an active layer 64 made of undoped GaInP or AlGaInP is arranged thereon.

On the active layer 64, a Mg-doped p-type AlGaInP cladding layer 65 and a Mg-doped p-type AlGaInP intermediate layer 67 are arranged and etched in a mesa shape. The side surface of the mesa is filled with an n-type GaAs region 66.

A p-type AlGaAs contact layer 68 doped with Mg or a p-type GaAs contact layer doped with Zn is arranged on these layers. An n-side electrode 69 is formed on the bottom surface of the n ⁺ type GaAs substrate 61,
A p-side electrode 70 is formed on the upper surface of the p-type AlGaAs contact layer 68. The composition of the clad layers 63 and 65 is (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P.

When manufacturing the visible light semiconductor laser shown in FIG. 4, a normal MOV is formed on the n ⁺ type GaAs substrate 61.
According to PE, grow up to the active layer 64 and p
In the growth of the mold layer, crystal growth is carried out while mixing and doping the organometallic compound of Mg and the organometallic compound of Al as a p-type dopant.

Therefore, as compared with the visible light semiconductor laser of the conventional example shown in FIG. 5A, Al is added also to the intermediate layer 67 where it is not necessary to add Al. Zn can usually be doped in high concentration with respect to GaAs in the contact layer, and Zn-doped GaAs may be used. Alternatively, Mg-doped AlGaAs may be used.

Not only the illustrated structure but also a structure in which a plurality of AlGaInP group III-V group p-type semiconductor layers are connected to each other, an Mg organometallic compound is added as a p-type dopant and at the same time an Al organometal is added. Add the compound,
The Mg doping delay is reduced.

Below, at the same time as the organometallic compound of Mg,
The effect of crystal growth performed by supplying the organometallic compound of 1 will be described more specifically. FIG. 6A shows the configuration of the sample used to verify the effect of Mg doping. Zn
Zn-doped GaA on the doped GaAs substrate 91
The s buffer layer 92 is grown to form a base substrate for growing Mg-doped crystals.

While doping Mg on this base substrate,
(Al _x Ga _1-x ) _0.5 In _0.5 P first intermediate layer 93 (x
= 0 to _0.4 ), (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P
Second intermediate layer 94, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
The clad layer 95 is sequentially grown. First intermediate layer 93, second
The composition of the intermediate layer 94 is the buffer layer 92 and the cladding layer 95.
The valence bands between are selected so as to connect smoothly.

The substrate temperature during growth is 650 ° C. to 800 ° C.
Select from the range. For example, GaAs is 670 ° C,
The temperature of AlGaInP is 670 to 730 ° C. (varied depending on the composition of Al).

FIG. 6B shows that without adding Al as a dopant (ie, the composition of the above-mentioned intermediate layer 93 (Al
_x Ga _1-x ) _0.5 In _0.5 P with x = 0), Mg
The result when only Cp ₂ Mg is doped as the source gas of is shown. In the figure, the horizontal axis represents the depth from the surface in microns, and the vertical axis represents the hole concentration.

GaIn is formed on the GaAs regions 91 and 92.
A P layer 93 is grown to a thickness of 0.2 μm and (Al _0.4 Ga
_{A 0.6} ) _0.5 In _0.5 P layer 94 was grown to about 300Å, and an (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer 95 was grown thereon to a thickness of about 0.5 μm.

As is clear from the carrier distribution in the figure, Z
From the n-doped GaAs region into the GaInP layer 93 thereabove, the hole concentration drops sharply. afterwards,
In the vicinity of the layer 94 of (Al _x Ga _1-x ) _0.5 In _0.5 P (x = 0.4), the hole concentration has a high value, and eventually stabilizes at a substantially constant value. For example, if the hole concentration decreases by one digit, the resistance increases by one digit.

As described above, when the hole concentration is insufficient in the growth layer in which the high-concentration p-type region is formed, the IV characteristic of the resulting semiconductor device deteriorates. Figure 7
A and FIG. 7B show the results when trimethylaluminum TMA was added at the same time as Mg source Cp ₂ Mg.

In FIG. 7A, M is in contact with the GaAs layer.
Considering that Mg was not immediately doped even when trying to grow a g-doped GaInP layer, Al was mixed from the beginning in order to allow the occurrence of band discontinuity.

Zn-doped GaAs regions 91, 92
On top of it, while doping Al with Mg, (Al _x Ga
AlGaInP layer 93 in which the composition x of _1-x ) _0.5 In _0.5 P is gradually increased from 0.04 to 0.4, (Al _0.4 Ga
_0.6 ) _0.5 In _0.5 P layer 94 is grown, and (Al
_{A 0.7} Ga _0.3 ) _0.5 In _0.5 P layer 95 was grown. The thickness of each layer is the same as in FIG. 6B.

In this case, the hole concentration is G doped with Zn.
AlGaI doped with Mg from aAs regions 91 and 92
Once it entered nP93, 94, it slightly dropped, but recovered immediately, and thereafter showed a substantially uniform high concentration. M
The width of the region where the hole concentration dropped into the g-doped region was about 270Å. However, even in this region, the hole concentration is about 1 × 10 ¹⁸ cm ⁻³ or more, which is a sufficiently high concentration as compared with the case of FIG. 6B.

FIG. 7B shows an example in which the amount of Al mixed in from the beginning is further increased. While doping Al with Mg, the composition gradient of the (Al _x Ga _1-x ) _0.5 In _0.5 P layers 93 and 94 was changed from x = 0.1 to x = 0.4.

The hole concentration distribution in this case shows the same tendency as in FIG. 7A, but the initial drop in the Mg-doped region is shallower and narrower. The width of the region where the hole concentration dropped was about 150Å.

The result of FIG. 7A is satisfactory for p-type layer growth, and the result of FIG. 7B is extremely satisfactory. From this result, it is understood that when using the organometallic compound of Mg as the dopant, it is preferable to add the organometallic compound of Al at a predetermined amount or more at the same time.

The amount of Al to be added is (Al _x Ga _{1 -x} )
In the case of _0.5 In _0.5 P, at least x = 0.04 (Al _0.02 as the composition), and preferably x = 0.1 (Al composition is Al _0.05 when considering the entire group III elements).
It should be noted that the amount of Al mixed is set to Al for all Group III element raw materials.
_{It is preferably 0.1} or less so that the physical properties of the semiconductor layer are not substantially changed.

FIG. 8 shows triethylaluminum T as an organometallic compound of Al added to the organometallic compound of Mg.
The result when EA is used is shown. The grown composition is (A
l _x Ga _1-x ) _0.5 In _{0.5 As the} P layer 93, x = 0.0
It was set to 4.

Similar to the result of FIG. 7A, the obtained hole concentration distribution slightly drops in the initial stage of the AlGaInP layer 93, but is a value of about 1 × 10 ¹⁸ cm ⁻³ or more, and then rises rapidly and is almost It shows a constant high concentration.
It can be seen that when TEA is used as the organometallic compound of Al, the amount of Al to be added is about the same as that of TMA.

As described above, the AlGaInP system III-V
Cp ₂ as a p-type dopant in a group compound semiconductor
When Mg and an Al organometallic compound (TMA or TEA) are used at the same time, a high hole concentration of about 1 × 10 ¹⁸ cm ⁻³ or more can be obtained, and the hole concentration is 1 to 3 × 10 ¹⁸ c.
It was able to be almost constant as m ^-3 . Compared with the case of conventional Mg doping, the doping delay is significantly improved.

Although Al is introduced into the crystal by applying Al, the amount is on the order of 10 ²⁰ cm ^-3 , and the density of group III atoms in the crystal is about 2 × 10 ²² cm 3.
Compared with ^-3 , there are no practical problems.

The amount of the Al organometallic compound to be added to the Mg organometallic compound as the p-type dopant is M
It depends on the desired dopant concentration of g. FIG. 9A shows
6 is a graph showing the results of doping delay when the ratio of the molar flow rate of the Mg raw material to the molar flow rate of the Group III raw material is changed with the composition of the Al element raw material relative to the total Group III raw material of the growth layer as a parameter. In the figure, the circles indicate the data obtained with good reproducibility and no doping delay.
The mark shows the data that sometimes resulted in the doping delay, and the X mark always shows the data that resulted in the doping delay.

As is apparent from the figure, when the molar flow ratio of the Mg raw material to the molar flow rate of the Group III raw material is about 2 × 10 ⁻³ or more, the composition of the Al element raw material to the total Group III element raw material is about 0. At 0.02, the doping delay can be substantially eliminated, and the doping delay can be significantly reduced even with an extremely low solid phase composition.

When the molar flow rate ratio of the Mg raw material to the molar flow rate of the Group III raw material is about 1 × 10 ⁻³ , the doping is performed by adjusting the composition of the Al element raw material to the total Group III element raw material to about 0.02 or more. The delay can be remarkably reduced, and if the composition of the Al element raw material with respect to the total group III element raw material is set to about 0.03 to 0.035 or more, the doping delay can be substantially eliminated.

For lower Mg raw material molar flow ratios:
The composition of the Al element raw material to be added to the total group III element raw material has a larger value. FIG. 9B shows the experimental results of Mg doping delay in a wider Al mixed region. The horizontal axis represents the amount of Al element raw material (TMA or TEA) relative to the total group III element raw material, and the vertical axis represents the amount of Mg raw material (Cp ₂ Mg) relative to the total group III element raw material.
The results with a doping delay are shown by ●, and the cases without a doping delay are shown by ○.

The condition that does not cause the doping delay can be judged to be a region above the solid curve p. It can be seen that when the amount of Mg to be added increases, the doping delay hardly occurs, and when the amount of Al to be mixed increases, the doping delay does not occur. In addition, the amount of Al to be mixed is II
If it is about 0.05 or more with respect to the group I element, the effect on the delay of Mg doping is considered to be almost constant.

In order not to change the characteristics of the base material, Al
It is preferable that the added amount of Al is smaller, and the added amount of Al is preferably 0.05 or less with respect to the amount of all Group III element raw materials added for Mg doping.

As described above, when Mg is used as the p-type dopant, a predetermined amount or more of Al is added to the organometallic compound of Mg.
It became possible to reduce the doping delay to such an extent that there is practically no problem by mixing the organometallic compound.

FIG. 10 shows an SBW type visible light semiconductor laser according to an embodiment of the present invention. Zn-doped p-type GaAs
The substrate 111 has a stripe-shaped mesa structure formed on its surface. On this GaAs substrate 111, an Se-doped n-type GaAs current block layer 112 is formed so as to fill the side surface of the mesa, thereby forming a mesa structure with a step difference relaxed.

On this mesa structure, Zn-doped p-type G
The aAs buffer layer 113 is epitaxially grown. This configuration is equivalent to that shown in FIG. 5B.
On the buffer layer 113, Mg-doped p-type (Al _{x
Ga 1-x) 0.5 In 0.} 5 P of the intermediate layer 114a is formed epitaxially. The composition x of this layer is gradually changed from x = 0.04 to x = 0.4 from the side in contact with the buffer layer to form a composition gradient layer.

Mg-doped p-type A is formed on the intermediate layer 114a.
The lGaInP cladding layer 115a is epitaxially grown. The composition of the clad layer is (Al _0.7 G
a _{0. 3)} is _0.5 In _0.5 P.

Non-doped G is formed on the cladding layer 115a.
The aInP active layer 116 is epitaxially grown, and the n-side stack is epitaxially grown thereon. The n-side stack includes an Se-doped n-type AlGaInP cladding layer 117 on the active layer, a Se-doped n-type GaInP intermediate layer 118 thereon, and a Se-doped n-type GaAs contact layer 119 thereon. The stack up from the active layer 116 is equivalent to the configuration shown in FIG. 5B.

In this structure, the intermediate layer 114a and the cladding 115a are Mg-doped, and the intermediate layer 1
The point that 14a is formed of a composition gradient layer is different from FIG. 5B.

Regarding other knowledge of such SBW laser, US patent application USSN 892,680, European patent application
See 91303783.4 (EP-A 454476). In this configuration, since the intermediate layer is formed of a layer containing Al and is doped with Mg, the entire intermediate layer can be highly doped with Mg. On the side in contact with the buffer layer 113,
Since the composition x of Al is set to 0.04, it contains Al, but its physical property is almost the same as that of GaInP, and the addition of Al does not substantially change.

Heterojunction bipolar transistor (HB
T) is a transistor that uses a material with a wider bandgap than the base and collector for the emitter, and is noted as a basic element for the next-generation ultra-high-speed integrated circuit due to its high gain, high drive capability, and high speed. I am collecting.

In order to improve the high speed operation characteristics of the HBT, it is necessary to increase the carrier concentration in the base region as much as possible to reduce the base resistance and to make the base film thickness as thin as possible to shorten the carrier transit time. Is.

For doping HBT into the base, Zn, Be, C, Mg or the like is used depending on the crystal growth method (MBE method, CBE method, MOCVD method, etc.). Zn is a commonly used dopant in other devices, but HBT
In that case, it is difficult to obtain the required high carrier concentration, and since diffusion in the crystal is very large, it is difficult to form a thin base region.

Be can be highly doped, but
The problem is that, once again, diffusion in the crystal occurs, which is even more toxic. From such a background, expectations for C and Mg, which are capable of high-concentration doping, have small diffusion, and have no toxicity problem, are currently increasing.

A problem in using Mg for HBT is a doping delay. HB made of III-V compound semiconductor
T is mainly AlGaAs / GaAs / GaAs system, In
P / InGaAs / InGaAs system, InAlAs / I
Although it is an nGaAs / InGaAs system (emitter / base / collector), the base is made of a material containing no Al in any system.

Furthermore, the thickness of the base region is usually several hundreds.
Since it is about Å, Mg is hardly incorporated in the base due to the doping delay even if Mg is introduced into the crystal.

FIG. 11 shows a hetero bipolar transistor according to an embodiment of the present invention. An n-type collector region 122, a p-type base region 123, and an n-type emitter region 124 are stacked on the substrate 121.

GaAs can be used as the substrate 121, the collector region 122 can be formed of GaAs, the base region 123 can be formed of Mg-doped AlGaAs, and the emitter 124 can be formed of AlGaAs.

Here, for the base region 123, the amount of Mg to be doped is determined according to the desired carrier concentration, and the Mg
The composition of Al to be mixed to dope without causing a doping delay is selected with reference to FIG. 9B, for example. The mixing amount of Al was 0.
1 or less.

The substrate 121 is made of InP, the collector region 122 is made of InGaAs, and the base region 1 is made of InP.
23 may be formed of Mg-doped AlInGaAs and the emitter region 124 may be formed of InP.

At this time, the amount of Mg doped in the base region 123 is determined by the p-type impurity concentration desired in the base region, and the amount of Al mixed is such that the Mg doping does not cause a doping delay and the amount of Al in the base region is large. Select within the range that does not substantially change the physical properties.

It is also possible to form the substrate 121 with InP, the collector region 122 with n-type InGaAs, the base region 123 with Mg-doped AlInGaAs, and the emitter region 124 with InAlAs.

By mixing a trace amount of Al raw material when crystal-growing the base, it is possible to eliminate the doping delay and to perform sharp high-concentration doping on the thin base region. At this time, since the amount of Al introduced into the base material is sufficiently small, the band gap difference between the emitter and the base is sufficiently secured, and the operation of the HBT is not impaired. Also, Al
The introduction of recombination defects due to oxygen impurities, which are likely to bond with, does not impair the device characteristics.

When an erbium-doped optical fiber is excited with light having a specific wavelength, light having another wavelength propagating in the fiber can be amplified. Attention has been focused on long-distance optical communication utilizing this optical fiber amplification.

Although there are several kinds of wavelengths of light used for excitation, it is known that 0.98 μm light has the highest amplification efficiency among them. From this background, the wavelength 0.98
There is an increasing demand for semiconductor lasers that oscillate at μm.

FIG. 12 is a typical sectional structure view of a semiconductor laser having a wavelength of 0.98 μm. In principle, a 0.98 μm wavelength semiconductor laser cannot be produced with a mixed crystal material system that is completely lattice-matched to an InP or GaAs substrate.
Therefore, it is necessary to use a special combination in which the active layer is intentionally lattice-mismatched.

In FIG. 12, 131 is Si-doped n-type Ga.
As substrate, 132 is Si-doped n-type AlGaAs or GaInP cladding layer, 133 is Si-doped n-type GaAs guide layer, 134 is InGaAs strained quantum well active layer, 135 is Mg-doped p-type AlGaAs guide layer, and 136 is Mg-doped p-type AlGaAs cladding layers and 137 are Zn-doped p-type GaAs contact layers.

The composition and thickness of each layer are as follows, for example. Cladding layers 132, 136: Al _0.7 Ga _0.3 As or In _0.5 Ga _0.5 P, 1-2 μm. n-type guide layer 133: GaAs, 0.1 μm. Active layer 134: In _0.2 Ga _0.8 As, 50
.About.100 Å p-type guide layer 135: Al _0.1 Ga _0.9 As, 0.
1 μm. Contact layer 137: GaAs, 0.5-1 μm. The band gap of GaAs is 1.42 eV, which corresponds to a wavelength of 0.87 μm. In in the GaAs active layer
The wavelength can be extended to about 1 μm by introducing

At this time, the lattice constant deviates as it becomes larger than that of GaAs. However, if the film thickness of InGaAs is less than the critical value, generation of dislocation due to lattice mismatch can be suppressed.

To obtain a wavelength of 0.98 μm,
The composition is In_0.2Ga_0.8As to In _0.3Ga_0.7As
The critical film thickness at this time is about 50 to 100Å
It This laser has the effect of compressive strain introduced into the active layer,
Device characteristics (threshold current density,
Very good).

Sufficient light output is required to excite the optical fiber. One of the conditions for obtaining a high light output is to reduce the resistance of the element and reduce the heat generation during operation. For this purpose, it is necessary to increase the carrier concentration of the AlGaAs cladding layer, especially the p-type AlGaAs cladding layer.

The p-type dopant in p-type AlGaAs is generally Zn, but Zn has a problem that the diffusion in the crystal is very large and the active layer is damaged.

On the other hand, Mg has the advantage that high-concentration doping equivalent to that of Zn is possible and that diffusion in the crystal is smaller than that of Zn. When Mg is used as the p-type impurity, it is ideally desired to dope the GaAs guide layer with Mg, but a significant doping delay occurs in Mg doping of GaAs.

Therefore, when the upper GaAs guide layer 135 is grown, by adding a trace amount of Al raw material, M
It is possible to eliminate the g-doping delay and obtain a steep doping profile from the vicinity of the active layer.

Mg of the guide layer 135 and the cladding layer 136
Carrier concentration is 5 × 10¹⁷cm ^-3-1 x 10¹⁸cm
^-3, Guide layer Al_xGa_1-xThe Al composition of As is x =
It is about 0.1. The Al composition at this time impairs the light distribution.
Not a thing.

The reason why the doping delay is reduced is as follows.
It is considered that this is due to the interaction between the organometallic compound of Mg and the organometallic compound of Al, and it is considered that it does not depend on the composition other than Al of the III-V group compound semiconductor to be grown.

Therefore, the AlGaInP system III-V
When adding Mg as a p-type dopant to other III-V group compound semiconductors as well as group III compound semiconductors,
The above method is considered effective.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various changes, improvements, combinations and the like can be made.

[0123]

As described above, according to the present invention,
By mixing the organometallic compound of Al with the organometallic compound of the raw material of Mg during the doping of Mg,
Mg can be effectively introduced into the crystal from the beginning of doping.

In particular, it is possible to solve the Mg doping delay, which has been a problem in the growth of Al-free III-V group compound semiconductor crystals such as GaInP and GaAs. Therefore, a p-type region such as a visible light semiconductor laser using an AlGaInP-based III-V group compound semiconductor can be formed by Mg doping.

[Brief description of drawings]

FIG. 1A is a schematic view showing a method for manufacturing a semiconductor device according to the basic concept of the present invention.

FIG. 1B is a sectional view schematically showing a semiconductor device according to the basic concept of the present invention.

FIG. 2 is a block diagram showing a CVD crystal growth system for carrying out a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a CVD crystal growth system for carrying out a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a configuration example of a visible light semiconductor laser.

FIG. 5A is a cross-sectional view showing a configuration example of a visible light semiconductor laser according to a conventional technique.

FIG. 5B is a cross-sectional view showing a configuration example of a visible light semiconductor laser according to a conventional technique.

FIG. 5C is a graph showing a dopant concentration distribution for explaining a doping delay in Mg doping.

FIG. 5D is a cross-sectional view showing a configuration example of a semiconductor visible light laser device manufactured according to a conventional technique.

FIG. 6A is a schematic sectional view showing the structure of a sample of a Mg doping experiment conducted by the present inventors.

FIG. 6B is a graph showing a result of doping Mg without adding Al.

FIG. 7A is a graph showing a result of producing a sample shown in FIG. 6A by adding TMA to Cp ₂ Mg and performing p-type doping.

FIG. 7B is a graph showing a result of producing a sample shown in FIG. 6A by adding TMA to Cp ₂ Mg and performing p-type doping.

FIG. 8 is a graph showing the results of producing a sample shown in FIG. 6A by adding TEA to Cp ₂ Mg and performing p-type doping.

FIG. 9A is a graph showing the degree of doping delay depending on the amount of an organometallic compound of Al added at the time of doping an organometallic compound of Mg.

FIG. 9B is a graph showing the degree of doping delay depending on the amount of Al organometallic compound added during doping of Mg organometallic compound.

FIG. 10 is a sectional view of an SBW structure semiconductor laser according to an embodiment of the present invention.

FIG. 11 is a sectional view of a hetero bipolar transistor (HBT) according to an embodiment of the present invention.

FIG. 12 shows an oscillation wavelength of 0.98 μm according to an embodiment of the present invention.
3 is a sectional view of the semiconductor laser of FIG.

[Explanation of symbols]

 1 Organometallic compound of Mg 2 Organometallic compound of Al 3 Other raw material 6 Base substrate 7 Growth layer doped with Al together with Mg 8 p-side electrode or p-type substrate 9 Base layer 11 Reaction tube 12 Susceptor 13 Base substrate 15 Gas switching Manifold 16, 17 Valve 18 Interlocking switching valve 21 Supply pipe 22 Waste pipe 31, 35, 41, 45 Mass flow controller 34, 44 Pressure control valve 36, 46 Pressure gauge 38, 48, 59 Control line 51, 56, 56a Mass flow controller 57 Pressure control valve 58 Pressure gauge

Claims (11)

[Claims] 1. An MO of a p-type III-V group compound semiconductor layer.
In VPE crystal growth, a mixed gas of an organometallic compound of Mg and an organometallic compound of Al is used as a p-type impurity, and Al is included as a group III element in the vicinity of the interface in the initial stage of growth in an amount of about 0.02 to about 0.1. A method for manufacturing a semiconductor device, which comprises a step of growing an Mg-doped p-type layer. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the organometallic compound of Mg and the organometallic compound of Al are mixed under a first pressure to form a mixed dopant gas, A method of manufacturing a semiconductor device, comprising the step of mixing the mixed dopant gas with another source gas under a second pressure lower than the first pressure and supplying the mixed source gas onto a base substrate for crystal growth. 3. The organometallic compound of Mg is biscyclopentadienyl magnesium or bismethylcyclopentadienyl magnesium, and the organometallic compound of Al is trimethylaluminum or triethylaluminum. Manufacturing method of semiconductor device. 4. A mixed gas of an organometallic compound of Mg and an organometallic compound of Al is used as a p-type impurity source on a Zn-doped p-type GaAs base crystal, and the Al composition is about 0.02 or more as a group III element. First AlGa of 0.1 or less
A step of crystal-growing an InP layer by metalorganic vapor phase epitaxy, and using a mixed gas of an organometallic compound of Mg and an organometallic compound of Al as a p-type impurity source on the first AlGaInP layer, And a step of crystallizing a second AlGaInP layer having a higher Al composition than the AlGaInP layer by metal organic chemical vapor deposition. 5. Further, the composition of the second AlGaInP layer is approximately (Al) by using a mixed gas of an organometallic compound of Mg and an organometallic compound of Al as a p-type impurity source.
_0.7 Ga _0.3 ) _0.5 In _0.5 P and a third AlGaI
The method for manufacturing a compound semiconductor device according to claim 4, comprising a step of growing an nP layer. 6. A base compound semiconductor crystal layer is formed on the crystal layer.
Mg as a p-type impurity and Al as a group III element
P-type III- which contains about 0.02 or more and about 0.1 or less
A second p-type III layer formed on the group V compound semiconductor layer and the first p-type group III-V compound semiconductor layer, containing Mg as a p-type impurity and containing Al having a higher composition as a group III element. A III-V compound semiconductor device including a -V compound semiconductor layer. 7. The base compound semiconductor crystal layer has a surface of GaAs doped with Zn as a p-type impurity, and the first p-type III-V compound semiconductor layer is p-type (Al
_x Ga _1-x ) _0.5 In _0.5 As layer, and the second p
The III-V compound semiconductor device according to claim 6, wherein the type III-V compound semiconductor layer is a p-type AlGaInP layer. 8. The III according to claim 6, wherein the second p-type III-V group compound semiconductor layer is a p-type AlGaInP layer having a composition gradient in which the Al composition gradually increases.
-Group V compound semiconductor device. 9. The base compound semiconductor crystal layer is an undoped InGaAs layer, and the first p-type III-V layer is used.
Group compound semiconductor layer is p-type AlGaAs layer or p-type Ga
The III-V compound semiconductor device according to claim 6, which is an InP layer. 10. A base compound semiconductor crystal layer not doped with Mg, formed on the base compound semiconductor crystal layer, containing Mg as a p-type impurity, and containing Al as a group III element in an amount of about 0.0.
A p-type III-V group compound semiconductor layer containing 2 or more and about 0.1 or less, and an n formed on the p-type III-V group compound semiconductor layer.
III-V group compound semiconductor device having a type III-V group compound semiconductor layer. 11. The base compound semiconductor crystal layer is p-type I.
The n-type III-V group compound semiconductor layer is an n-type AlGaAs layer, an n-type InP layer, and an n-type InA.
11. The III according to claim 10, which is any one of 1As layers.
-Group V compound semiconductor device.