JPH0936426A - Method for producing group 3-5 compound semiconductor - Google Patents

Abstract

(57) Abstract: A method for producing a Group 3-5 compound semiconductor capable of increasing the brightness and the luminous efficiency of a light emitting device is provided. A general formula In _x Ga _y Al _z N (x + y + z
= 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), and includes at least one p-type layer in the stacked structure. A Group 3-5 compound semiconductor containing layers is grown in a reaction tube by a metalorganic vapor phase epitaxy method using a Group 3 organometallic compound and a compound having N in the raw material as a raw material to produce a Group 3-5 compound semiconductor. A method for producing a Group 3-5 compound semiconductor, comprising the step of supplying a p-type dopant material and not supplying a Group 3 material before the step of growing the p-type layer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is based on a vapor phase growth method.
-5 Group compound semiconductor manufacturing method. In particular, the present invention relates to a method for manufacturing a 3-5 group compound semiconductor used for a light emitting device.

[0002]

2. Description of the Related Art Conventionally, a general formula In _x Ga _y Al _z N (where x + y + z = 1,0) is used as a blue light emitting diode.
≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) 3-5
Those using group compound semiconductors are used. The 3-
Group 5 compound semiconductors are of a direct transition type and thus have high emission efficiency, and can emit light with emission wavelengths from yellow to violet and ultraviolet regions depending on the In concentration. Therefore, they are particularly useful for short wavelength light emitting device applications.

As a method for producing the 3-5 group compound semiconductor, a molecular beam epitaxy (hereinafter sometimes referred to as MBE) method, a metal organic chemical vapor deposition (hereinafter sometimes referred to as MOVPE) method, Hydride vapor phase growth (hereinafter, HV
Sometimes referred to as PE. ) Method is used. Among them, the MOVPE method is a method in which a substrate placed under normal pressure or reduced pressure is heated to form an organic metal compound containing a Group 3 element and
In this method, a raw material containing a group element is supplied in a vapor phase state to cause a thermal decomposition reaction on a substrate to grow a semiconductor film. This MOVPE method is important in that it is possible to grow a uniform and high-quality 3-5 group compound semiconductor on a large area.

By the way, as a method of increasing the luminous efficiency of a light emitting device, a light emitting layer is sandwiched between p-type and n-type semiconductor layers.
It is widely known to use a so-called double hetero structure in which a layer having a band gap larger than that of the light emitting layer is in contact with each other on both sides of the light emitting layer.
However, since it is very difficult to form a steep pn junction interface in a 3-5 group compound semiconductor manufactured by the MOVPE method, even in an element having a double hetero structure,
The brightness and luminous efficiency were still insufficient.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a Group 3-5 compound semiconductor capable of increasing the brightness and luminous efficiency of a light emitting device.

[0006]

Means for Solving the Problems The present inventors
As a result of various studies on a light emitting device having a double hetero structure of a group compound semiconductor, in order to improve the steepness at the growth interface of the p-type layer, a p-type dopant material is supplied before growing the p-type layer. It was found that the luminous efficiency of the light emitting element was dramatically improved by providing a step of not supplying the group raw material (hereinafter, sometimes referred to as a blank flow step), and the present invention was completed.

That is, the present invention is the invention described below. [1] general formula _{In x Ga y Al z N (} x + y + z = 1,
0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) 3-
A group III-V compound semiconductor including a layered structure of a group V compound semiconductor, in which at least one p-type layer is included in the layered structure, using a group III organometallic compound and a compound having N in the molecule as raw materials. , A method for producing a Group 3-5 compound semiconductor by growing in a reaction tube by metalorganic vapor phase epitaxy,
A method for producing a Group 3-5 compound semiconductor, comprising a step of supplying a p-type dopant material and not supplying a Group 3 material before the step of growing the p-type layer. [2] The method for producing a Group 3-5 compound semiconductor according to [1], wherein the p-type dopant is Mg.

[3] A Group 3-5 compound semiconductor comprises an n-type first layer, a p-type second layer, and at least one third layer sandwiched between the two layers. And the third layer is in contact with two layers having a bandgap larger than the third layer on both sides of the third layer. [1] or [2]
-5 Group compound semiconductor manufacturing method. [4] The method for producing a Group 3-5 compound semiconductor according to [3], wherein the third layer has a layer thickness of 5 Å or more and 90 Å or less. [5] Si, Ge, Mg, Z contained in the layer of the third layer
Each of the concentrations of n and Cd is 1 × 10 ¹⁹ cm ⁻³ or less, and the method for producing a Group 3-5 compound semiconductor according to [3], wherein

Next, the present invention will be described in detail. The 3-5
Since good crystals cannot be obtained by bulk growth of group III compound semiconductors, it is difficult to perform homoepitaxial growth using the group III-5 compound semiconductor itself as a substrate. Therefore, sapphire, ZnO, GaAs, Si, SiC or the like is used as a substrate for crystal growth of the Group 3-5 compound semiconductor. In particular, sapphire is preferable because the group 3-5 compound semiconductor having good crystallinity can be grown by using a buffer layer such as AlN.

In the present invention, the following raw materials are used.
Can be. Trimethylgallium as Group 3 raw material
[(CH_Three)_ThreeGa, sometimes referred to as TMG
You. ], Triethylgallium [(C_TwoH_Five)_ThreeGa, less
Sometimes referred to as a lower TEG. General formula R such as₁R_TwoR_Three
Ga (where R₁, R_Two, R_ThreeIs a lower alkyl group
You. ) Trialkylgallium represented by
Luminium [(CH_Three)_ThreeAl], triethylaluminium
Umm [(C_TwoH_Five)_ThreeAl, sometimes referred to as TEA below
You. ], Triisobutylaluminum [(i-C
_FourH₉) _ThreeAl] etc.₁R_TwoR_ThreeAl (here
R₁, R_Two, R_ThreeRepresents a lower alkyl group. )
Trialkyl aluminum; trimethylamine alane
[(CH_Three)_ThreeN: AlH_Three]; Trimethylindium
[(CH_Three)_ThreeIn, sometimes referred to as TMI below
You. ], Triethylindium [(C_TwoH_Five)_ThreeIn]
General formula R such as₁R_TwoR_ThreeIn (where R₁, R_Two, R_Three
Represents a lower alkyl group. ) Trialkyl group represented by
And the like. These can be used alone or as a mixture
Used.

Next, examples of the Group 5 raw materials include ammonia, hydrazine, methylhydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine, ethylenediamine and the like. These may be used alone or as a mixture. Among these raw materials, ammonia and hydrazine do not contain a carbon atom in the molecule, so that the contamination of the semiconductor with carbon is small and suitable. The 3
As the p-type dopant of the -5 group compound semiconductor, a 2 group element is preferable. Specifically, Mg, Zn, Cd, Hg, Be
Among these, Mg is preferable because it is easy to form a low resistance p-type.

As the raw material of the Mg dopant, biscyclopentadienyl magnesium (hereinafter sometimes referred to as Cp ₂ Mg), bismethylcyclopentadienyl magnesium, bisethylcyclopentadienyl magnesium, bis n-propyl. Tables represented by general formula (RC ₅ H ₄ ) ₂ Mg (wherein R represents H or a lower alkyl group having 1 to 4 carbon atoms) such as cyclopentadienyl magnesium and bis i-propylcyclopentadienyl magnesium. The organometallic compounds mentioned are suitable because they have a suitable vapor pressure.

The n-type dopant of the 3-5 group compound semiconductor is preferably a group 4 element or a group 6 element. Specifically, S
Examples thereof include i, Ge, and O. Among these, Si is preferable because n-type with low resistance is easily formed and a material with high purity is obtained. As a raw material of the Si dopant, SiH ₄ ,
Si ₂ H _{6 and the} like are preferable.

The method for producing a group 3-5 compound semiconductor of the present invention is characterized by including a step of supplying a p-type dopant material and not supplying a group 3 material before the step of growing the p-type semiconductor layer. Do (empty process). As shown in the conceptual diagram of FIG. 1, this idling step is a step performed before the step of growing the p-type layer, supplies the p-type dopant material, and
This is a process in which no group raw material is supplied. The flushing step and the subsequent p-type layer growth step may be performed continuously or at time intervals (in the case of FIG. 1), but in order to prevent a change in crystal quality, the time interval is Is preferably as short as possible and is preferably carried out continuously. The flow rate of the p-type dopant material in the blank-flow step may be the same as or different from the flow rate of the p-type dopant material in the step of growing the p-type layer. Since there is a risk that the quality of the crystal will deteriorate if the flow rate fluctuates, it is preferable that the flow rate does not fluctuate.

The temperature in the reaction tube in the idling step may be the same as or different from the growth temperature of the p-type layer to be performed thereafter, but the same temperature is more preferable. When the temperature of the idling process is different from the growth temperature of the p-type layer, the growth time is lengthened by the time required for raising or lowering the temperature, and during the idling process while the temperature is changed. This is not preferable because the quality of the grown crystal may deteriorate. The pressure in the reaction tube in the idling step may be the same as or different from the pressure during the subsequent growth of the p-type layer, but the same pressure allows both steps to be performed continuously and the growth Since the complexity of the process can be reduced, the Group 5 source gas may or may not be supplied at the same time in the more preferable empty flow step. However, the temperature of the idling process is 65
When the temperature is 0 ° C or higher, if the Group 5 source gas is not supplied,
Since the quality of the crystals grown before this step may deteriorate, it is preferable to supply the Group 5 source gas at the same time.

The main control factor in the idling process is p
Type of dopant material, flow rate, supply time, temperature and pressure. Since the preferable range of these control factors varies depending on the growth apparatus, it is not possible to specify the preferable range unconditionally, but as the growth apparatus becomes larger, the flow rate in the preferable range increases and the supply time becomes longer. Change direction.

As an example of the preferable range of the flow rate of the Mg raw material, the range in the apparatus used by the present inventors will be given.
When biscyclopentadienyl magnesium is used, the carrier gas flow rate is 50 sccm or more and 500 sccm or less with the raw material bubbler kept at 30 ° C. If it is less than 50 sccm or more than 500 sccm, the effect of providing this step cannot be obtained, which is not preferable. Here, sccm is a unit of the flow rate of the gas, and shows that a weight of gas occupies a volume of 1 cc in a standard state per minute.

As a preferable example of the Mg raw material supply time, the range in the apparatus used by the present inventors is 110.
When the idling process using biscyclopentadienylmagnesium is carried out under the conditions of 0 ° C., atmospheric pressure and a flow rate of 200 sccm, it is 1 second or more and less than 3 minutes, more preferably 10 seconds or more and 2 minutes or less. If it is shorter than 1 second or longer than 3 minutes, the effect of this step cannot be obtained, which is not preferable. The preferred temperature range of the idling step is 600 ° C or higher and 1200 ° C or lower. Even if the temperature is lower than 600 ° C. or higher than 1200 ° C., the effect of this step cannot be obtained, which is not preferable.

As a 3-5 group compound semiconductor obtained by the method for producing a 3-5 group compound semiconductor of the present invention, an n-type first layer and a second layer doped with a p-type dopant,
One having a structure in which a third layer which is a light emitting layer is sandwiched is given. Charges can be injected from the first layer and the second layer, and the charges can be recombined in the third layer to emit light. In particular, a so-called double hetero structure in which the third layer is sandwiched in contact with two layers having a larger band gap than this has the effect of confining charges in the third layer.
It is preferable because the luminous efficiency can be increased. However, when there is an n-type layer between two or more p-type layers in the laminated structure,
Or if there is a p-type layer between two or more n-type layers,
Since pn junctions opposite to each other can be formed in the laminated structure, the electrical characteristics of the diode are deteriorated, which is not preferable. When the band gap of the 3-5 group compound semiconductor exceeds 5 eV, the resistance becomes high and it becomes difficult to move charges. Therefore, the band gap of all layers of the 3-5 group compound semiconductor is 5 eV or less. Preferably there is. In order to efficiently confine charges in the third layer by the double hetero structure in the Group 3-5 compound semiconductor of the present invention, the band gap of the two layers in contact with the third layer is 0 than the band gap of the third layer. It is preferably larger than 0.1 eV. More preferably, it is 0.3 eV or more.

The third layer may be a layer composed of a plurality of layers functioning as a light emitting layer. A specific example in which a layer composed of a plurality of layers functions as a light emitting layer is a structure in which two or more light emitting layers are stacked with a layer having a larger band gap.

The third layer, which is a light emitting layer, is preferably a Group 3-5 compound semiconductor having an In composition of 10% or more because it has a bandgap in the visible region and is therefore suitable for display applications. Those containing Al easily take in impurities such as oxygen, and when used as a light emitting layer, the luminous efficiency may be lowered. In such a case, the general formula In containing no Al as the light emitting layer is used.
_x Ga _y N (provided that, x + y = 1,0 <x ≦ 1,0 ≦ y
The thing represented by <1) can be utilized.

The lattice constant of the group 3-5 compound semiconductor is
Change significantly depending on the success. In particular, the lattice constant of InN is G
About 12% larger than aN or AlN
Yes. Therefore, the composition of each layer of the Group 3-5 compound semiconductor is
Therefore, a large difference occurs in the lattice constant between layers.
Sometimes. Crystal defects if there is a large lattice mismatch
May occur, which causes deterioration of crystallinity.
In order to suppress the occurrence of defects due to lattice mismatch, lattice mismatch
Do not reduce layer thickness depending on the amount of strain due to matching.
I have to. The preferred thickness range is the amount of strain
Dependent. Ga _xAl_1-xN (however, 0 ≦ x ≦ 1)
Layered with the Group 3-5 compound semiconductor containing 10% or more of In
In this case, the preferable thickness of the layer containing In is 5 Å or more and 50
It is less than 0Å. The thickness of the layer containing In is smaller than 5Å
In this case, the luminous efficiency becomes insufficient. Also, from 500Å
If it is large, defects will occur and the luminous efficiency will not be sufficient.
It becomes. More preferable thickness range is 5 Å or more and 90 Å or less
Below.

By doping the third layer with impurities, it is possible to emit light at a wavelength different from the band gap of the third layer. Since this is light emission from impurities, it is called impurity light emission. In the case of impurity emission, the emission wavelength is the third
It depends on the composition of the Group 3 element of the layer and the impurity element. In this case, the In composition of the third layer is preferably 5% or more. In
When the composition is less than 5%, the emitted light is mostly ultraviolet rays, and sufficient brightness cannot be felt. In
The emission wavelength becomes longer as the composition is increased, and the emission wavelength can be adjusted from purple to blue and green. Impurities suitable for light emission are preferably Group 2 elements. Among the Group 2 elements, doping with Mg, Zn, and Cd is preferable because the luminous efficiency is high. Zn is particularly preferable. The concentration of these elements is preferably 10 ¹⁸ to 10 ²² cm ⁻³ . The third layer may be simultaneously doped with Si or Ge together with these Group 2 elements. The preferable concentration range of Si and Ge is 10 ¹⁸ to 10 ²² cm ⁻³ .

In the case of impurity emission, the emission spectrum generally becomes broad, and the emission spectrum shifts as the amount of injected charges increases, and a band edge emission peak appears, which is not preferable. It is difficult to increase luminous efficiency. Therefore, it is advantageous to use band edge emission when high color purity is required, when it is necessary to concentrate emission power in a narrow wavelength range, or when a device having high emission efficiency is required. .
In order to realize a light emitting element by band edge emission,
The amount of impurities contained in the layer must be kept low. Specifically, the concentration of each element of Si, Ge, Mg, Cd, and Zn is preferably 10 ¹⁹ cm ^-3 or less, more preferably 10 ¹⁸ cm ^-3 or less. In the case of band edge emission, the emission color is determined by the composition of the Group 3 element of the third layer. When light is emitted in the visible region, the In composition is preferably 10% or more. When the In composition is less than 10%, most of the emitted light is ultraviolet light, and sufficient brightness cannot be felt. The emission wavelength becomes longer as the In composition increases, and the emission wavelength can be adjusted from purple to blue and green.

When the third layer which is the light emitting layer contains In,
The thermal stability is not sufficient, and deterioration may occur during crystal growth or in the semiconductor process. For the purpose of preventing such deterioration of the light emitting layer, between the light emitting layer and the p-type layer,
A protective layer may be included. In order to provide a sufficient protective function, the In composition of the protective layer is preferably 10% or less and the Al composition is preferably 5% or more. More preferably, the In composition is 5% or less and the Al composition is 10% or more. The thickness of the protective layer is 10
It is preferably Å or more and 1 μm or less. More preferably, 50
It is Å or more and 5000 Å or less. If the film thickness of the protective layer is less than 10Å, a sufficient effect cannot be obtained. On the other hand, when it is larger than 1 μm, the luminous efficiency is reduced, which is not preferable.

[0026]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 A 3-5 group compound semiconductor having the structure shown in FIG. 2 was prepared by the MOVPE method, and a light emitting device was prepared therefrom. As the substrate, a sapphire C surface mirror-polished was used after organic cleaning. The growth was performed by a two-step growth method using a low temperature growth buffer layer. At a substrate temperature of 550 ° C., hydrogen is used as a carrier gas, and TMG and ammonia are supplied to form a Ga film having a film thickness of 500 Å.
The N buffer layer 2 was formed. Next, the substrate temperature is set to 1100.
C., TMG, ammonia and silane gas are supplied onto the buffer layer 2 to have an n-type carrier concentration of 1 × 10 ¹⁹ / cm ³ with Si as a dopant and a film thickness of about 3 μm.
m GaN layer 3 is grown, and TMG,
Ammonia is supplied to remove the undoped GaN layer 4 to 15
00Å grew up.

Next, the substrate temperature was lowered to 785 ° C., the carrier gas was changed to nitrogen, and TEG, TMI and ammonia were added at 0.04 sccm, 0.08 sccm and 4 respectively.
In _0.3 Ga _0.7 N layer 5 serving as a light emitting layer by supplying slm
Were grown for 70 seconds. Furthermore, TEG, T at the same temperature
EA and ammonia 0.032sccm,
The Ga _0.8 Al _0.2 N layer 6 as a protective layer was grown for 10 minutes by supplying 0.008 sccm and 4 slm. However,
slm is a unit of gas flow rate and 1 slm is 1000 sc
Corresponds to cm. Regarding the layer thickness of these two layers, since the growth rates obtained from the thickness of the layer grown for a longer time under the same conditions are 43Å / min and 30Å / min, the layer thickness obtained from the above growth time is They are 50Å and 300Å respectively.

Next, the substrate temperature is raised to 1100 ° C. and C
After performing p ₂ Mg and ammonia empty supply to 40 seconds flowing step, TMG, a GaN layer 7 doped with Mg by supplying Cp ₂ Mg and ammonia 5000Å
grown. After taking out the group 3-5 compound semiconductor sample produced as described above from the reaction furnace, it was kept in nitrogen at 800 ° C. for 2
Annealing treatment was performed for 0 minutes to make the Mg-doped GaN layer into a low-resistance p-type layer. An electrode was formed on the thus obtained sample by a conventional method to obtain an LED. Ni-Au as p electrode
An alloy and Al were used as the n electrode. When a current was applied to this LED in the forward direction, clear blue light emission with an emission wavelength of 4570Å was shown. The brightness at 20 mA was 1240 mcd.

Comparative Example 1 A comparative sample was prepared in the same manner as in Example 1 except that the blank flow step of supplying Cp ₂ Mg and ammonia was not performed. When a current was applied to this, blue light emission with an emission wavelength of 4400Å was observed, but the luminance at a forward direction of 20 mA was 390 mcd.

Examples 2 and 3, except that the time period of the blank flow step of supplying Cp ₂ Mg and ammonia was changed from 40 seconds to 30 seconds (Example 2) and 60 seconds (Example 3), Semiconductors and LEDs were produced in the same manner as in Example 1. When a current was applied to this LED in the forward direction, clear blue light emission was exhibited. 20m
Table 1 shows the luminance, efficiency, and emission wavelength at A.

COMPARATIVE EXAMPLE 2 Except that the time of the blank flow step of supplying Cp ₂ Mg and ammonia was changed from 40 seconds to 180 seconds,
A sample for comparison was grown in the same manner as in Example 1. When a current was applied to this, no blue luminescence was visually observed. FIG. 3 shows the relationship between the time of the idling process and the luminance at 20 mA. From this figure, it can be seen that the brightness of 30 seconds, 40 seconds, and 60 seconds is significantly improved as compared with the case where no flow is performed.

[0032]

[Table 1]

[0033]

According to the present invention, by providing the step of supplying the p-type dopant raw material and not supplying the group 3 raw material before the growth of the p-type Group 3-5 compound semiconductor layer,
Since a light-emitting element with improved luminance and luminous efficiency can be manufactured, it is extremely useful and has great industrial value.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an idling process in the present invention.

FIG. 2 is a diagram showing a structure of a Group 3-5 compound semiconductor shown in Example 1 of the present invention.

FIG. 3 is a diagram showing the relationship between the time of the idling process of the Mg raw material and the brightness of the LED in Examples 1 to 3 and Comparative Examples 1 and 2.

[Explanation of symbols]

 1 ... Sapphire substrate 2 ... GaN buffer layer 3 ... n-type GaN: Si layer 4 ... Non-doped GaN layer 5 ... 1st layer n-type GaN layer 6 ... 3rd layer InGaN layer 7 ... AlGaN layer that is a protective layer 8 ... p-type GaN: Mg layer that is the second layer

Claims (4)

[Claims] 1. A general formula In _x Ga _y Al _z N (x + y + z
= 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), and includes at least one p-type layer in the stacked structure. A Group 3-5 compound semiconductor containing layers is grown in a reaction tube by a metalorganic vapor phase epitaxy method using a Group 3 organometallic compound and a compound having N in the raw material as a raw material to produce a Group 3-5 compound semiconductor. A method for producing a Group 3-5 compound semiconductor, comprising the step of supplying a p-type dopant material and not supplying a Group 3 material before the step of growing the p-type layer. 2. A Group 3-5 compound semiconductor comprises an n-type first layer, a p-type second layer, and at least one third layer sandwiched between the two layers. The method for producing a Group 3-5 compound semiconductor according to claim 1, wherein the third layer is in contact with two layers having a band gap larger than the third layer on both sides of the layer. 3. The method for producing a Group 3-5 compound semiconductor according to claim 2, wherein the layer thickness of the third layer is not less than 5Å and not more than 90Å. 4. Si, Ge, M contained in the layer of the third layer
Each concentration of g, Zn and Cd is 1 × 10 ¹⁹ cm
^{It is -3} or less, The manufacturing method of the 3-5 group compound semiconductor of Claim 2 or 3 characterized by the above-mentioned.