JPH0334536A - Manufacture of iii-v compound semiconductor element - Google Patents

Abstract

PURPOSE:To execute a steep magnesium doping operation with good controllability and to obtain a III-V compound semiconductor element, with good reproducibility, which simultaneously achieves a low threshold value, a high output and high reliability by a method wherein an organic metal compound which contains both magnesium and oxygen is used as a doping source of magnesium. CONSTITUTION:A III-V compound semiconductor element is manufactured by using trimethylgallium (TMG), trimethylaluminum (TMA), triethylboron (TEB) and trimethylindium (TMI) as organic compounds of group III metals, by using phosphine (PH3), arsine (AsH3) and ammonia (NH3) as group V hydrides and by using silane (SiH4) and Mg(thd)2 as doping sources. Desired raw-material gases are caused to flow through individual reaction tubes 11, 12, 13 of an MOCVD apparatus, of a multichamber system, which is used for this manufacture; a substrate 15 is moved by using a computer-controlled motor. Thereby, a sharp concentration change can be realized easily. It is not required to change over reaction gases at high speed in order to form a steep heterointerface.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a ■-V group compound semiconductor device, and more specifically, a p-type compound semiconductor device doped with magnesium.
The present invention relates to a method for manufacturing a ①-① group compound semiconductor device, which includes a step of forming a -v group compound semiconductor layer by organometallic vapor phase epitaxy.

(Prior Art) When producing a p-type ■-V group compound semiconductor by metal organic chemical vapor deposition (MOCVD), zinc is usually used as a p-type dopant. Zinc shows very good doping properties as a dopant for GaAs, but InP.

When used as a dopant for a ■-V group compound semiconductor containing phosphorus, such as GalnAIP, not only the incorporation rate is low but also the activation rate is low.

Moreover, the diffusion rate is too fast and the controllability is poor.

Therefore, attempts have been made to use beryllium or magnesium as a p-type dopant in place of zinc. However, although beryllium exhibits good properties as a p-type dopant in molecular beam epitaxial growth, its organic compound exhibits strong toxicity, so M
Application to OCVD methods must be avoided.

Organic compounds of magnesium have fewer toxicity problems than organic beryllium compounds. As such organic magnesium, alkylmagnesium compounds such as dimethylmagnesium and diethylmagnesium can be considered, but these alkylmagnesium compounds have very strong self-association properties and do not have the effective vapor pressure necessary for MOCVD. In addition, biscyclopentadienylmagnesium (C92Mg), which has a cyclopenta ring and has a relatively high vapor pressure, is used; It is very difficult to control doping, and it is not possible to ensure the steepness of a concentration change of three orders of magnitude or more within 0.1 μm, which is normally required for devices. Furthermore, there is an example of using bismethylcyclopentagenylmagnesium ((CH3)2C1)2Mg), which has a methyl group introduced into the cyclopenta ring, in order to increase the vapor pressure, but the concentration change is not sufficiently steep. Not obtained.

(Problems to be Solved by the Invention) As described above, the conventionally used magnesium doping sources have a high memory effect, making it difficult to do steep doping.

Therefore, the present invention makes it possible to perform p-type doping with excellent controllability by organometallic vapor phase epitaxy by using an organomagnesium compound with weak self-association and no memory effect as a magnesium doping source.
An object of the present invention is to provide a method for manufacturing a -V group compound semiconductor device.

[Structure of the Invention] (Means for Solving the Problems) The method for manufacturing a ■-V group compound semiconductor device according to the present invention includes:
When forming a p-type m-V group compound semiconductor layer doped with magnesium by organometallic vapor phase epitaxy, the present invention is characterized in that an organometallic compound containing both magnesium and oxygen is used as a magnesium doping source.

(Effect) According to research conducted by the present inventors on various organomagnesium compounds, the memory effect of C92Mg is as follows:
It has been confirmed through doping using many organomagnesium compounds that this is not an essential problem common to organomagnesium compounds, but rather a problem specific to magnesium compounds having a certain type of cyclopenta ring. Among them, oxygen-containing organomagnesium compounds such as bis(2
,2,6,6-tetramethyl-3,5-heptanedionate-o,o'>Magnesium (Mg(thd)z)
, bis(2,4-pentanedionato-〇,O')magnesium (Mg(AcAc)2), CH3C5
H4Mg (CO) 3 and the like showed good doping characteristics with no memory effect observed.

Magnesium dope sources containing oxygen have not been used in the past due to concerns about oxygen contamination.

In particular, in compounds containing aluminum, the Al-0 bond is very strong, so a large amount of oxygen is mixed in, and it has been thought that compounds containing oxygen are not suitable as magnesium dope sources. However, it has been found that even in organomagnesium compounds containing oxygen, contamination with oxygen can be avoided depending on the structure.

That is, Mg(AcAc) which is a β-diketone compound
2 and Mg(thd)2 are each represented by the following formula, Mg(AcAc)2 Mg(thd)2 Certain cyclic compounds such as β-diketone compounds have Mg- Bonds between 0 are more easily broken than other bonds, and mixing of oxygen during doping can be avoided. Furthermore, since these compounds do not have a cyclopenta ring, no memory effect occurs.

Thus, in the present invention, the magnesium-doped p
By using an organometallic compound containing both magnesium and oxygen as a magnesium doping source when forming a conductor layer of type 2-v, steep doping can be performed with good reproducibility.

(Example).

Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 1 shows a multi-chamber type MOCVD apparatus used for manufacturing the ■-v group compound semiconductor device of the present invention. This device consists of a reaction tube 11.1 made of quartz.
2 and 13, and the necessary raw material gas is taken in from the gas inlets located at the top of each. These reaction tubes 11, 12 and 13 are vertically attached to one chamber 14 through its upper cover. The substrate 15 is
Each reaction tube 1 is installed on a graphite susceptor 16.
1.12.13, and is heated to a high temperature by an external high frequency coil 17. The susceptor 16 is attached to a quartz holder 18 and is connected to each reaction tube 11.12.1 by means of a drive shaft 19 via a magnetic fluid seal.
3 at a high speed of about 0.1 seconds, for example. The drive is performed by an externally installed computer-controlled motor. A thermocouple 20 is placed in the center of the susceptor 16 to monitor the temperature directly below the substrate. A slip ring is used in the cord portion to prevent twisting due to rotation. The reaction gas is
The hydrogen gas is pushed out by the fast downward flow from the upper jet port 21, and the hydrogen gas is exhausted from the exhaust port 22 by the rotary pump while mixing with each other is suppressed as much as possible.

By using such an MOCVD apparatus, a desired raw material gas is flowed through each reaction tube 11, 12, 13, and the substrate 15 is moved by a computer-controlled motor, thereby forming a multilayer film with an arbitrary lamination period and an arbitrary composition. Structures can be fabricated on substrate 15. With this method, sharp concentration changes that cannot be obtained with the gas switching method can be easily achieved. In addition, with this method, there is no need to switch the reaction gas at high speed to create a steep hetero-interface, so the problem of slow decomposition speed of the raw material gases NH3 and PH3 can be solved by setting the gas flow rate low. be able to.

Using the MOCVD apparatus shown in FIG. 1, the ■-v group compound semiconductor devices shown in FIGS. 2 to 8 were fabricated. The raw materials used were trimethylgallium (TMG) and trimethylaluminum (organic compounds of group II metals).
TMA),) ethylboron (TEB), and trimethylindium (TMI) were used, phosphine (PH3), arsine (A s H3), and ammonia (NH3) were used as group V hydrides, and silane (SiH4) was used as a doping source. ), Mg(thd)2 were used.

FIG. 2 is a schematic cross-sectional view of an m-v group compound semiconductor device manufactured by the above method at a substrate temperature of 750° C., a reaction tube internal pressure of 25 Torr, a growth rate of 3 μm/hour, and a reaction tube flow rate of 70 cm/sec. This device consists of a p-type GaAs substrate (1
xlO19cm-3), on which p-type GaAs
Buffer layer 32 (0.5pm, 1xlO18cm-3
), p-type 1 n 6. g (G a I-, XAlx
) o, v; 4 layers 33 (1μm11X1o18cm-3)
n-type 1 n(4S(G a 1-XA I X ) o,
5 P layer 34 (1 μm.

1xlO17cm-3) is formed and on top of layer 34, n
Type QaAs contact layer 35 (2μm, 1x1017
cm −3) is formed. Ohmic electrodes 36 and 37 are formed on both sides of the element, respectively. These ohmic electrodes are connected to a power source 38.

When the obtained wafer was separated and a diode was fabricated, the identification factor was close to 1 and good 1-V characteristics were exhibited. In addition, M near the p-n junction interface
When SIMS analysis of
A sharp change in concentration of 103 or more was observed in 0.00. A constant carrier concentration of I x 101B was ensured in the nine layers.

FIG. 3 is a sectional view showing a schematic structure of a semiconductor laser device manufactured by the method of the present invention.

This laser device has an n-type GaAs substrate 41, on which an n-type GaAs buffer layer 42 and an n-type GaAs buffer layer 42 and an n-type GaAs buffer layer 42 are formed.
A type 1nGaP buffer layer 43 is formed. On the buffer layer 53, an n-type InGaAIP cladding layer 4.1nGaP active layer 45 and a p-type InGaAIP cladding layer 45 are formed.
A double heterojunction structure is formed of the series rad layers 46, 47, and 48. Here, the cladding layer 47 has a low Al composition and acts as an etch stop layer.

Further, the cladding layer 48 is processed into a striped shape, thereby forming striped ribs in the p-type cladding layer. On the cladding layer 48, p-type 1nGaA
An IP intermediate bandgap layer 49 is formed. An n-type GaAs current blocking layer 51 is formed on the side surface of the double heterojunction, and a p-type GaAs contact layer 52 is formed thereon. Further, a metal electrode 53 is formed on the upper surface of the contact layer 52, and a metal electrode 54 is formed on the lower surface of the substrate 41. In this structure, current confinement is achieved by the intermediate bandgap layer 49 and the current blocking layer 51.
The leading wave is generated by a cladding layer 48 formed in a striped mesa.

The wafer thus obtained was separated and the cavity length was 250μ.
When a laser device of m was fabricated, the threshold current was 40 m.
A. Good characteristics with a differential quantum efficiency of 20% per side were obtained. The optical output increased linearly to 10 mW or more according to the drive current, showing good current-light output characteristics without kinks. In addition, both the far-field and near-field images are unimodal,
It was found that good mode control was performed. The operating voltage was as low as 2.1V, and furthermore, an extremely long life of 10,000 hours was obtained. In this way, by performing good doping with good controllability, it was possible to obtain a semiconductor laser with good reproducibility that simultaneously achieves a low threshold value, high output power, and high reliability.

FIG. 4 is a cross-sectional view of a semiconductor laser device obtained by the method of the present invention, similar to the above.
The laser device shown in FIG. 3 is achieved by the contact layer 50.

Furthermore, a laser device having the structure shown in FIG. 5 can be similarly manufactured by the method of the present invention.

6 to 8 show cross-sectional views of other compound semiconductor devices manufactured by the method of the present invention. These elements are composed of GaAIBNP-based materials. In order to fabricate these devices, the substrate temperature is 850 to 115°C.
0℃, pressure 0.3 atm, total flow rate of raw material gas 1 liter/
The gas flow rate was adjusted so that the growth rate was 1 μm/hour. The specific flow rates of each source gas are TEB1xlO=mol/min, TMA5xlO-7 mol/min, TMG 5
xlo-7 mol/min, phosphine 5xlO=mol/min, ammonia 1xlO-3 mol/min. In addition, G
The typical stacking period for fabricating the aAIN/BP superlattice layer is 20 layers, and the heat ratio of the nitride layer and boride layer is 1:1.
In the following examples, this value was set unless otherwise specified. Although values other than this can be used, if the ratio of the layer thickness of GaAIN to BP of the light emitting layer becomes smaller than 1, the band structure changes from a direct transition type to an indirect transition type, and the luminous efficiency decreases. Also, the stacking period is not limited to the above value, but if it exceeds 50, electrons,
Since hole localization becomes noticeable and conductivity decreases, 50
It is desirable to set the period to less than Å.

Now, FIG. 6 shows a cross section of another semiconductor laser device. This laser device has an n-type GaP substrate 71, on which an n-type GaP buffer layer 72 and an n-type BP buffer layer 73 are formed. On the buffer layer 73 are an n-type Ga x A 11-XN/BP multilayer cladding layer 74 , an undoped GaxAt, -xN/BP multilayer active layer 75 , and a p-type Ga x A 11-8N/BP multilayer cladding layer 76 . A double heterojunction is formed. Note that an n-type BP current blocking layer 77 is formed on the RAD layer 76 so as to leave a stripe-shaped portion in the center thereof. On current blocking layer 77 and cladding layer 76
The p-type BP contact layer 7 covers the exposed striped surface of the p-type BP contact layer 7.
8 is formed. Further, a metal electrode 79 and a metal electrode 80 are formed on the upper surface of the contact layer 78 and the lower surface of the substrate 71, respectively. In this structure, a current blocking layer 77 is provided around the lower convex portion of the contact layer 78.
, current narrowing and leading wave can be realized in a self-aligned manner.

Now, the laser device shown in FIG. 6 is manufactured as follows. Using the MOCVD apparatus shown in FIG. 1 and under the conditions described above, first,
N-type GaP substrate 71 (Si doped, 1xlO1Bcm-
3) On top, an n-type GaP buffer layer 72 (Si doped,
lx1018cm-31μm), n-type BP buffer layer 7
3 (Si-doped, 1x1017cm-31μm), n-type Gao, 4At,,6N/BP multilayer cladding layer 74 (Si-doped, 1x1018cm-31μm)
m), undoped Ga 6.5' A 160. sN
/BP multilayer active layer 75 (0,1um), and p
Type ca,,+A I,,6N/BP multilayer cladding layer 76 (Mg doped, 1x1018cm-31μm
) was grown on double hetero wafers. Subsequently, a 5i02 film mask in the form of stripes with a width of 5 μm is formed on the cladding layer 76 by thermal decomposition of silane gas and photolithography, and an n-type BP current blocking layer 77 (Si doped, 1×101
8cm-31um) on only the top surface of the cladding layer 76.
After selective growth using the CVD method, the 5i02 film was removed. Next, a p-type BP contact layer 7g (
Mg-doped, 1x1018 cm-31 μm) was grown.

After that, a normal electrode mounting method is used to place an A u /Z n electrode 79 on the contact layer 78 and then on the substrate 7 .
A laser wafer having the structure shown in FIG. 6 was obtained by depositing an A u/G e electrode 80 on the lower surface of the wafer 1.

When the resulting wafer was separated and a laser device with a cavity length of 300 μm was fabricated, the pulse width was 1 at liquid nitrogen temperature.
With 00 μs pulse operation! i Colored laser oscillation was confirmed. At that time, the threshold current density is approximately 50 kA/cm
2 was shown. Moreover, it operated stably for more than 100 hours.

FIG. 7 shows a modification of the semiconductor device shown in FIG. 6.

The cladding layer 76 of the double heterojunction similar to that shown in FIG. 6 is processed into a convex shape, and has a lateral refractive index difference with equal polarization C)
By doing so, transverse mode control is performed. On the cladding layer 76, an n-type B
A P current blocking layer 77 is formed. Other structures are
It is similar to that in FIG. In the structure shown in FIG. 7, since the current blocking layer 77 is formed around the convex portion of the second conductivity type cladding layer 76, current confinement and refractive index type leading wave can be realized in a self-aligned manner.

To manufacture the device shown in FIG. 7, a similar double hetero wafer was grown using the MOCVD apparatus shown in FIG. 1 under the same conditions as the device manufacturing conditions shown in FIG. A 5i02 film mask is formed in a stripe shape with a width of 5 μm by thermal decomposition and photolithography, and the cladding layer 76 is
A striped mesa with a width of 3 μm was formed by etching. Next, an n-type BP current blocking layer 77 (Si doped, 1
x 1018 cm-31 μm) was selectively grown only on the upper surface of the cladding layer 76 by MOCVD. After that, 5
The i02 film was removed and a p-type BP contact layer 78 (Mg doped, 1×10 18 cm −31.5 μm) was grown. Thereafter, electrodes were attached, and a laser wafer having the structure shown in FIG. 7 was obtained.

When the resulting wafer was cleaved to fabricate a laser device with a cavity length of 300 μm, the pulse width was 1 at liquid nitrogen temperature.
Green light laser oscillation was confirmed with a pulse operation of 00 microseconds. At that time, the threshold current density was approximately 70 kA/cm2. Although the threshold current density was somewhat high, a single-peak far-field pattern was confirmed, indicating that good transverse mode control was performed. It also operated stably for over 100 hours.

FIG. 8 shows a light emitting device (
LE D) is a cross-sectional view. A p-type GaP buffer layer 92 and a p-type BP buffer layer 93 are formed on a p-type GaP substrate 91.
are sequentially formed, and p-type Ga A I N /
BP superlattice layer 94, undoped GaAIN/BP
A superlattice layer 95 and an n-type GaAIN/BP superlattice layer 96 are sequentially laminated, and an n-type GaN contact layer 97 is further formed thereon. Ohmic electrodes 98 and 99 are formed on both sides of the device wafer. This LED can also be manufactured in the same manner as above.

Although the present invention has been described above with reference to preferred embodiments, the present invention should not be limited to these embodiments. For example, in the above embodiment, Mg(t
hd)2 was used, but Mg(AcAc)2),
CH3C5H, s Mg (CO)3, etc. can also be used.

Further, the present invention is applicable to GaAs-based, InP-based, GaAl-based,
InGaAsP system, InGaA IP system, InGa
It can be applied to the production of various elements such as semiconductor lasers, LEDs, FETs, and HBTs made of AlAs-based, InGaAs-based, InAlAs-based, and other various ■-v group compound semiconductor materials.

Further, as the MOCVD raw materials, triethyl gallium (TEG) can be used as the Ga raw material, triethyl aluminum (TEA) can be used as the AI raw material, and trimethyl boron (TMB) or diborane (B2H6) can be used as the B raw material. In addition to hydrazine, Ga (C2H5)* NH3, G
Organometallic compounds that are nitrogen-containing adducts such as a (CH3)3N.(CH3)3 can also be used. In addition, various modifications are possible without departing from the gist of the present invention.

[Effects of the Invention] As described above, when forming a p-type ■-V group compound semiconductor layer doped with magnesium by the MOCVD method according to the present invention by organometallic vapor phase epitaxy, magnesium and oxygen are used as a doping source for magnesium. By using an organometallic compound containing both of can do.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an organometallic vapor phase growth apparatus suitable for carrying out the present invention, and FIGS. 2 to 8 show different ■-V group compound semiconductor devices manufactured by the method of the present invention. Diagram showing. 11.12.13...Reaction tube, 15,31°41.7
1.91...Substrate

Claims (2)

[Claims] (1) In a method for manufacturing a III-V compound semiconductor device including a step of forming a p-type III-V compound semiconductor layer doped with magnesium by organometallic vapor phase epitaxy, magnesium and oxygen are used as a doping source for magnesium. characterized by using an organometallic compound containing both
A method for manufacturing a III-V group compound semiconductor device. (2) The method according to claim 1, wherein the organometallic compound is bis(2,2,6,6-tetramethyl-3,5-heptanedionate-0,0')magnesium.