JPH05206520A - Manufacture of p-type ii-vi compound semiconductor - Google Patents

Abstract

PURPOSE:To manufacture a low resistance P-type light-emitting element of purple color from blue color by a method wherein, after a P-impurity-doped II-VI compound semiconductor has been formed by a vapor growth method, an annealing treatment is conducted thereon at specific temperature or higher, or an electron beam irradiation is performed, and a cap layer is formed. CONSTITUTION:After P-impurity-doped II-VI compound semiconductor layer has been formed by a vapor growth method, it is annealed at the temperature higher than 300 deg.C. Also, after P-impurity-doped II-VI compound semiconductor layer has been formed, an electron beam is applied to the compound semiconductor layer. Besides, when an annealing treatment or an electron beam irradiation is conducted at 300 deg.C or higher, a cap layer may be formed on the P-impurity- doped II-VI compound semiconductor layer before conducting the above- mentioned treatment or operation for the purpose of suppressing the decomposition by heat of the II-VI compound semiconductor. The cap layer is a protective layer, and it can be formed into P-type of low resistance in reduced pressure or normal pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a p-type II-VI group compound semiconductor used in light emitting devices such as ultraviolet light emitting diodes, blue light emitting laser diodes, ultraviolet light emitting diodes, blue light emitting diodes, and the like. The present invention relates to a method for making a II-VI group compound semiconductor layer formed by doping a p-type impurity by a growth method into a p-type having a low resistance.

[0002]

2. Description of the Related Art ZnS is a candidate material for blue light emitting devices.
There are II-VI group compound semiconductors such as e, ZnS, CdS, and CdSe. Conventionally, it has been very difficult to obtain a p-type crystal from these II-VI group materials, which has been a major problem in producing a blue light emitting device.

As a method of stacking II-VI group compound semiconductors, a vapor phase growth method such as a metal organic compound vapor phase growth method (hereinafter referred to as MOCVD method) is well known. For example, the case of growing ZnSe by the MOCVD method will be briefly described. In this method, an organometallic compound gas {diethyl zinc (DEZ), hydrogen selenide (H ₂ S) is used as a reaction gas in a reaction container in which a GaAs substrate is installed.
e) or the like}, the crystal growth temperature is maintained at a temperature of about 350 ° C. to grow ZnSe on the substrate, and other impurity gases are supplied as necessary to supply the ZnSe semiconductor with n-type or This is a p-type stacking method. GaAs, ZnSe, etc. are generally used for the substrate. n
Cl is well known as the type impurity, and N is most well known as the p type impurity.

However, a blue light emitting device having a II-VI group compound semiconductor has not yet been put to practical use. Because the II-VI group compound semiconductor has a low resistance p
This is because it cannot be formed into a mold, and thus light emitting elements having various structures such as double hetero and single hetero cannot be formed. Even if a II-VI group compound semiconductor doped with a p-type impurity is grown by a vapor phase growth method, the obtained II-VI group compound semiconductor does not have a low resistance p-type, but has a resistivity of about 100 Ω. The reality is that the p-type has a high resistance of cm or more.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to make a II-VI group compound semiconductor doped with a p-type impurity into a p-type having a further lower resistance, thereby making it possible to manufacture a practical light-emitting device. The present invention provides a method for manufacturing a II-VI group compound semiconductor.

[0006]

First, the p-type II of the present invention is used.
A method of manufacturing a group-VI compound semiconductor is characterized in that after a II-VI group compound semiconductor layer doped with a p-type impurity is formed by a vapor phase growth method, annealing is performed at a temperature of 300 ° C. or higher. ..

Annealing
After forming the II-VI group compound semiconductor layer doped with the p-type impurity, the step may be performed in the reaction vessel, or the wafer may be taken out of the reaction vessel and used in an apparatus dedicated to annealing. The annealing atmosphere is in vacuum,
It is carried out in an inert gas atmosphere of N ₂ , He, Ne, Ar or the like, or a mixed gas atmosphere thereof, and most preferably, a Group II gas or VI which is pressurized at a decomposition pressure of the II-VI group compound semiconductor or higher at the annealing temperature. It is performed in an atmosphere of a group gas or a mixed gas thereof. Because group II or V
This is because pressurization as a Group I gas atmosphere can prevent the II-VI group compound semiconductor from decomposing during annealing.

Further, the present invention is based on I doped with p-type impurities.
After forming the I-VI group compound semiconductor layer, the compound semiconductor layer is irradiated with an electron beam. The electron beam irradiation can usually be performed using an electron beam irradiation device such as SEM or EPMA within an acceleration voltage range of 1 kV to 30 kV.

Furthermore, when annealing or electron beam irradiation is performed at 300 ° C. or higher, as a means for suppressing thermal decomposition of the II-VI compound semiconductor, it is formed on the II-VI compound semiconductor layer doped with p-type impurities. Alternatively, it may be performed after forming the cap layer. The cap layer is a protective film which is doped with p-type impurities II
-By forming it on a Group VI compound semiconductor, not only under pressure but also under reduced pressure and normal pressure, II-
The group VI compound semiconductor can be made to have a low resistance p-type without being decomposed.

To form the cap layer, after forming a II-VI group compound semiconductor layer doped with p-type impurities,
Subsequently, it may be formed in the reaction apparatus, or the wafer may be taken out from the reaction apparatus and formed by another crystal growth apparatus such as a plasma CVD apparatus. The material of the cap layer may be any material that can be formed on a II-VI group compound semiconductor and is stable at 300 ° C. or higher, and is preferably a II-VI group compound semiconductor, Si ₃ N 2. ₄ , SiO ₂ can be used, and the type of material is appropriately selected depending on the annealing temperature. The thickness of the cap layer is usually 0.01 to 5 μm. If it is thinner than 0.01 μm, the effect as a protective film is not sufficiently obtained, and if it is thicker than 5 μm, the cap layer is removed by etching after annealing, and p-type II
It is uneconomical because it takes time to expose the group VI compound semiconductor layer.

[0011]

FIG. 1 is a diagram showing that a ZnSe compound semiconductor layer doped with nitrogen atoms (N) as a p-type impurity is changed to a low-resistance p-type by annealing. This is done by using the MOCVD method to form a ZnSe layer with a film thickness of 4 μm by doping N on a GaAs substrate while flowing NH ₃ as a p-type impurity, then taking out the wafer and setting the annealing temperature in a nitrogen atmosphere. FIG. 6 is a diagram in which the holes are measured on the wafer after being changed and annealed for 10 minutes, and the resistivity is plotted as a function of the annealing temperature.

As can be seen from this figure, the resistivity of the ZnSe layer doped with N sharply decreases from above 300 ° C., and from 400 ° C. or above, it shows a substantially constant p-type characteristic of low resistance, and the annealing The effect is appearing. In addition,
The hole measurement results of the ZnSe layer not annealed and the ZnSe layer annealed at 400 ° C. or higher showed that the ZnSe layer before annealing had a resistivity of 600 Ω · cm and a hole carrier concentration of 1 × 10 ¹⁵ / cm ³ , but after annealing. ZnSe layer had a resistivity of 0.8 Ω · cm and a hole carrier concentration of 1 × 10 ¹⁸ / cm ³ . This figure also shows Zn
Although it is a diagram showing Se, it was confirmed that similar results were obtained also in ZnS, CdS, CdSe similarly doped with p-type impurities, or a mixed crystal thereof.

Further, the above ZnSe layer of 4 μm annealed at 400 ° C. was etched to a thickness of 2 μm, and hole measurement was performed. As a result, the hole carrier concentration was 1 ×.
The value was 10 ¹⁸ / cm ³ and the resistivity was 0.7 Ω · cm, which were almost the same values as before etching. That is, the ZnSe layer doped with the p-type impurity was p-type with low resistance throughout the entire region uniformly in the depth direction by annealing.

Further, the N-doped ZnSe semiconductor film grown by the MOCVD method is put in an electron beam irradiation apparatus,
The electron beam irradiation was performed at an acceleration voltage of 10 kV. Before the electron beam irradiation, the ZnSe layer had a resistivity of 600 Ω · cm and a hole carrier concentration of 1 × 10 ¹⁵ / cm ³ , whereas the ZnSe layer after the electron beam irradiation had a resistivity of 0.8 Ω · cm and a hole carrier concentration. The density was 1 × 10 ¹⁸ / cm ³ .

The reason why a low resistance p-type II-VI compound semiconductor can be obtained by annealing or electron beam irradiation is presumed to be as follows.

That is, in the growth of the II-VI group compound semiconductor layer, NH ₃ is generally used as the N source as the p-type dopant, and during the growth, NH ₃ is decomposed to form atomic hydrogen. Conceivable. It is considered that this atomic hydrogen binds with N doped as an acceptor impurity to prevent N from acting as an acceptor. Therefore, the II-VI group compound semiconductor doped with N impurities after the reaction has high resistance.

However, by performing annealing or electron beam irradiation after growth, hydrogen bonded in the form of NH is dissociated by heat by annealing or electron beam induction by electron beam irradiation to remove N impurities. The p-type II-VI group compound semiconductor having a low resistance can be obtained because it comes out of the doped II-VI group compound semiconductor layer and N normally functions as an acceptor. Therefore, it is not preferable to use a gas containing hydrogen atoms such as NH ₃ and H ₂ in the annealing atmosphere.

On the other hand, also in the case of electron beam irradiation, it is most reproducible and the resistance can be lowered with the accelerating voltage usually in the range of 1 kV to 30 kV, and the effect is large. 1k
If it is smaller than V, the energy of the electron beam becomes small, and sufficient energy for separating hydrogen atoms cannot be obtained, and the dissociation effect tends to be insufficient. If it is higher than 30 kV, the energy of electrons becomes very large, and the sample temperature is too high even if the emission current is low, and the sample is decomposed, which is very difficult to control.

[0019]

The present invention will be described in detail with reference to the following examples.

[Example 1] First, GaAs cleaned well
Place the substrate on the susceptor in the reaction vessel. After the chamber is evacuated, the substrate is heated to 600 ° C while flowing hydrogen gas.
Then, heat for 10 minutes to remove the oxide on the surface. After that, the temperature is cooled to 350 ° C., and Z
DEZ gas as an n source is 4.0 × 10 ⁻⁶ mol / min, Se
H ₂ Se gas as a source is 100 × 10 ⁻⁶ mol / min, and NH 3 gas is 200 × 10 as a N source as a p-type dopant.
^-6 mol / min, while flowing hydrogen gas as a carrier gas at 2.0 liters / min, the N-doped p-type ZnSe layer 60
Grow with a film thickness of 4 μm per minute. After growth p-type ZnSe
The result of the hole measurement was that the resistivity was 600 Ω · cm and the hole carrier concentration was 1 × 10 ¹⁵ / cm ³ , which was a high resistance.

Next, the grown wafer is taken out of the reaction container, placed in an annealing apparatus, and annealed by holding it at 400 ° C. for 20 minutes in a nitrogen atmosphere at atmospheric pressure.
The results of hole measurement of p-type ZnSe obtained by annealing showed excellent p-type characteristics with a resistivity of 0.8 Ω · cm and a hole carrier concentration of 1 × 10 ¹⁸ / cm ³ .

Example 2 In Example 1, the grown wafer was taken out of the reaction container, placed in an electron beam irradiation apparatus, and irradiated with an electron beam at an acceleration voltage of 10 kV. Hole measurement of p-type ZnSe obtained by electron beam irradiation showed that the resistivity was 0.7 Ω · cm and the hole carrier concentration was 1 ×.
It exhibited excellent p-type characteristics of 10 ¹⁸ / cm ³ .

[Embodiment 3] In Embodiment 1, after growing an N-doped ZnSe layer, Z is subsequently used as a cap layer.
The nSe layer is grown to a thickness of 0.1 μm.

Annealing is performed by an annealing apparatus as in the first embodiment. Then, by etching, a layer of 0.2 μm was removed from the surface, the cap layer was removed to expose the p-type ZnSe layer, and hole measurement was performed in the same manner. 10 ¹⁸ / cm ³
And showed excellent p-type characteristics.

Example 4 In Example 1, after the N-doped ZnSe layer was grown, the wafer was taken out of the reaction vessel and a SiO ₂ layer of 0.2 μm was formed as a cap layer on the wafer using a plasma CVD apparatus. It is formed with a film thickness.

Thereafter, the acceleration voltage is 15 k as in the second embodiment.
At V, electron beam irradiation is performed on the entire wafer while scanning the electron beam. After that, the SiO ₂ cap layer was removed with hydrofluoric acid, the p-type ZnSe layer was exposed, and the hole measurement was performed in the same manner. As a result, the resistivity was 0.6 Ω · cm and the carrier concentration was 2.0 ×.
It exhibited excellent p-type characteristics of 10 ¹⁸ / cm ³ .

[0027]

As described above, according to the method of the present invention, a II-VI group compound semiconductor which has not been a p-type having a low resistance even when doped with a p-type impurity is made a p-type having a low resistance. Therefore, it is possible to manufacture blue to violet light emitting devices having various structures using II-VI group compound semiconductors, and the industrial advantage is immeasurable.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an annealing temperature and a resistivity according to an embodiment of the present invention.

Claims (5)

[Claims] 1. A II-VI group compound semiconductor doped with a p-type impurity is formed by a vapor phase epitaxy method, and then 300 ° C.
A method for manufacturing a p-type II-VI group compound semiconductor, which comprises performing annealing at the above temperature. 2. A method for producing a p-type II-VI compound semiconductor, which comprises irradiating an electron beam after forming a II-VI compound semiconductor doped with a p-type impurity by a vapor phase growth method. 3. The annealing is performed in a group II or group V gas or a mixed gas atmosphere of group II and group V gas pressurized at a pressure equal to or higher than the decomposition pressure of the group II-VI compound semiconductor at the annealing temperature. The method for producing a p-type gallium nitride compound semiconductor according to claim 1. 4. II-VI doped with the p-type impurity
The p-type II-V according to claim 1 or 2, further comprising a cap layer formed on the group compound semiconductor.
Method of manufacturing group I compound semiconductor. 5. The p-type II-VI according to claim 4, wherein the cap layer is made of a material selected from the group consisting of II-VI group compound semiconductors, Si ₃ N ₄ and SiO _2. Group compound semiconductor manufacturing method.