JP2551376B2 - Method for manufacturing semiconductor superlattice - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a II-VI group compound semiconductor,
In particular, it relates to a method for manufacturing a ZnS-ZnTe superlattice.

[0002]

2. Description of the Related Art Since the announcement of a green-blue semiconductor laser, attention has been paid to II-VI group compound semiconductors having a large band gap represented by ZnSe. ZnSe
It was conventionally said that p-type doping is difficult, but in recent years, p-type ZnSe has come to be obtained by the N ₂ radical doping technique using the molecular beam epitaxy (MBE).

However, there are still many problems in the ZnSe type II-VI group compound semiconductor by MBE. First, it is difficult to control the composition of the mixed crystal. The reason is that the vapor pressure of the constituent elements of the II-VI group compound semiconductor is so high that it is difficult to control the vapor pressure. The second is that the hole concentration is low when a mixed crystal such as ZnSSe is used.

On the other hand, there is a superlattice structure as one of the wide-gap semiconductors whose doping can be controlled. In particular, a ZnS-ZnTe superlattice can realize a bandgap equivalent to that of ZnSe, and if a selective doped superlattice p-doped only in ZnTe is produced, a selective doped superlattice n-doped only in ZnS is produced. If you do n
Become a mold. The band gap can also be controlled by changing the thickness of each layer of the superlattice. Further, the metal organic chemical vapor deposition method (MOCVD) is very promising as a method for growing II-VI group compound semiconductors, because it can control the growth raw material extremely precisely and is excellent in mass productivity.

ZnS-ZnT using conventional MOCVD
A method for manufacturing an e-superlattice is described in detail in Applied Physics Letters (Appl. Phys. Lett.) 1992, Vol. 61, pp. 291-293. In this manufacturing method, the InP substrate is set in the MOCVD apparatus, and the substrate temperature is set to 450 ° C. Dimethyl zinc ((CH ₃ ) ₂ Zn; hereinafter referred to as DMZn) as a ZnS growth raw material
And hydrogen sulfide (H ₂ S) are used, DMZn and diethyl tellurium ((C ₂ H ₅ ) ₂ Te: hereinafter referred to as DETe) are used as ZnTe growth raw materials, and these are alternately supplied into the reaction tube. A ZnS-ZnTe superlattice layer is grown.

[0006]

The ZnS-ZnTe superlattice structure obtained by the conventional manufacturing method has a problem in the periodicity that the superlattice structure should have. Further, there is a problem that the film thickness uniformity on the substrate surface is poor. When the superlattice structure of each layer of ZnS and ZnTe produced by the conventional production method and having a thickness of 20 A (angstrom) was examined by X-ray diffraction, the X-ray satellite peak due to the periodicity of the superlattice structure was very weak. It was It is considered that this is because there is a problem in variation in film thickness in the growth layer thickness direction or in flatness of each layer.

When the film thickness of the semiconductors forming the superlattice is varied and the periodicity thereof is deteriorated, the quantum levels formed by the semiconductor having a small band gap are different in each layer, the coupling between these levels is weakened, and the emission intensity is increased. It is weak and broad.

On the other hand, in order to increase the band gap of the superlattice layer, it is necessary to reduce the thickness of each of the ZnS and ZnTe layers. However, in the conventional manufacturing method, ZnS, Z
There is a problem that it is difficult to produce a superlattice of nTe having a film thickness of a molecular layer (ML; monolayer) order.

The object of the present invention is to keep ZnS-ZnTe excellent in crystallinity while maintaining periodicity even in a film thickness of molecular layer order.
It is to provide a method for manufacturing a superlattice.

[0010]

In order to achieve the above object, the present invention uses a metalorganic vapor phase epitaxy method and contains II- containing sulfur (S) as one of the constituent elements of Group VI. In the superlattice growth of a group VI compound semiconductor and a group II-VI compound semiconductor containing tellurium (Te) as one of the constituent elements of the group VI, diisopropyl sulfur ((i-C ₃ H ₇ ) ₂ S; hereinafter referred to as DIPS), using diethyl tellurium (DETe) as a material for tellurium,
Alternatively diisopropyl tellurium _{((i-C 3 H 7} ) 2 T
e; hereinafter referred to as DIPTe) is used.

[0011]

The ZnS-ZnTe superlattice grown by the conventional method has a serious problem in its periodicity. The reason is that the used H ₂ S is an alkylzinc raw material (DMZn in this case).
This is because ZnS is likely to undergo nuclei growth even on the substrate surface and the surface of the growth layer becomes rough because of the nature of violent reaction in the gas phase. For the same reason as this, an ultra-thin film Z of several molecular layers
When nS was grown, the surface was not flat, and it was difficult to grow a superlattice of several molecular layers.

The DIPS of the present invention does not react directly with alkylzinc. At the same time, DETe and DIPTe also do not react with alkylzinc. In such a raw material system,
There is no nucleation on the substrate surface, and the flatness of the grown layer is very good.

Regarding DIPS, Journal Crystal Growth, 1992, Vol. 117, p. 119-
It is reported on page 124 as a CdZnS growth raw material. According to the report, when DIPS is used, the uniformity of the composition in the substrate surface is very poor, and the reproducibility of the composition control is also poor. At the same time, tertiary butyl mercaptan as sulfur feedstock _{(t-C 4 H 9 SH} ; hereinafter, referred to as TBSH) uniformity of the composition in the case of using,
It was reported that the reproducibility of composition control was excellent. Since this report, there has been no report on crystal growth using DIPS.

The present inventor has proposed that these DIPS and TBSH
The experiment of II-VI group compound semiconductor growth was carried out using. As a result of investigating by changing the growth conditions such as the growth temperature, the supply amount ratio of the group VI raw material and the group II raw material, the reaction tube pressure, etc., particularly when DIPS was used, the reaction tube pressure was reduced to about 1/5 or less of the atmospheric pressure. It was found that the uniformity of the film thickness was very good when it was set.
In addition, as a result of comparing the photoluminescence characteristics of ZnS grown using the respective raw materials, the emission obtained near the band edge is strongly observed from the sample obtained using DIPS, whereas the sample obtained from TBSH is generally observed. Emission from a deep level called SA emission was strongly observed, and it was found that the sample from DIPS had excellent crystallinity.

Next, these raw materials were used in the manufacture of semiconductor superlattices for comparison. As a result, DMZn, DIPS, DIP
When Te is used, the thickness of each layer is 2M which is composed of several ML.
Even when the LZnS-2ML ZnTe superlattice structure was manufactured, a clear X-ray satellite peak was observed,
The periodic structure of the superlattice was confirmed. On the other hand, DMZn, TB
When SH and DIPTe were used, X-ray satellite peaks were observed in all the prepared samples, but the peak intensity was weak, and only a very weak first-order satellite peak was observed in the 2ML ZnS-2MLZnTe superlattice structure. Was not done. It is considered that this is because the ZnS layer is rough because a small amount of TBSH causes a gas phase reaction with DMZn. From these results, it is particularly effective to use DIPS as a means for producing an ultrathin film superlattice in which the layer thickness of each II-VI group compound semiconductor constituting the semiconductor superlattice is 10 ML or less.

When DETe was used as a growth material of Te, good quality crystal growth was possible in ZnTe growth at a growth temperature of 400 ° C. or higher. Also, D
When IPTe was used, the growth was possible even at a low growth temperature of 300 ° C. Superlattice growth requires ultrathin film growth, but the lower the growth temperature, the better the flatness of the film and the more suitable it was for superlattice growth.

[0017]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an MOC used to explain this embodiment.
It is a schematic diagram of a VD device. The growth apparatus used was the reaction tube 1.
The substrate 12 installed in the substrate 1 is heated by induction heating of the high frequency coil 13. Also, the reaction tube 1
1 includes AsH ₃ and PH using H ₂ as a carrier gas.
_In addition to ₃ , a plurality of organic metals are supplied by bubbling H ₂ . In this embodiment, G is used as the substrate.
aAs is used as the design value (2ML ZnS-2ML
The case of growing ZnTe) × 200 cycles will be described. The growth procedure is as follows.

After setting the pressure in the reaction tube to 70 Torr, the substrate 12 is cooled to 5 while supplying AsH ₃ to the reaction tube 11.
The temperature was raised to 80 ° C., and the surface of the substrate was cleaned for 10 minutes. DMZn contained in the bubbler 1a was bubbled with H ₂ . Similarly, the DE stored in the bubbler 1b
Te, DIPS stored in the bubbler 1d, and tertiary butyl selenol (t
_{- (C 4 H 9) SeH} ; hereinafter, referred to as TBSeH) were respectively bubbled. Set the substrate temperature to 450 ° C,
After stopping the supply of AsH ₃ , first, DMZn and TBS
eH was supplied to the reaction tube 11, and the ZnSe buffer layer was added to 1.
6 μm was grown. The flow rate of DMZn at this time is 20 μm.
ol / min, the flow rate of TBSeH is 40 μmol / mi
n, and the total carrier flow rate was 2000 sccm.

After completing the growth of the ZnSe buffer layer, DMZ
While supplying n to the reaction tube 11, DIPS and DETe were alternately supplied to the reaction tube. The flow rate of DMZn at this time is 5μ
mol / min, DIPS flow rate is 30 μmol / mi
The flow rate of n and DETe is 20 μmol / min, and D
The supply times of IPS and DETe were 17 seconds and 8 seconds, and the gas non-supply (purging) time was 5 seconds.

For the obtained ZnS-ZnTe superlattice, X
As a result of line diffraction measurement, an X-ray satellite peak due to the superlattice structure was observed. One period of the superlattice structure obtained from the satellite peak was 12.8A, which was very close to the design value of 11.5A.

Example 2 As a raw material for tellurium, DIP was used.
The case of using Te will be described. The substrate is GaAs,
The design value of the superlattice is (4ML ZnS-2ML ZnT
e) x 200 cycles. The growth procedure is as follows.

After the pressure inside the reaction tube is set to 70 Torr, the substrate 12 is heated to 5 while supplying AsH ₃ to the reaction tube 11.
The temperature was raised to 80 ° C., and the surface of the substrate was cleaned for 10 minutes. DMZn contained in the bubbler 1a was bubbled with H ₂ . Similarly, D stored in the bubbler 1c
The IPTe, the DIPS contained in the bubbler 1d, and the TBSeH contained in the bubbler 1e were bubbled, respectively. After setting the substrate temperature to 330 ° C. and stopping the supply of AsH ₃ , first, DMZn and TBSeH were added to the reaction tube 1.
1, and a ZnSe buffer layer was grown to 1.6 μm. The flow rate of DMZn at this time is 20 mol / min, T
The flow rate of BSeH was 40 μmol / min, and the total carrier flow rate was 2000 sccm.

After completion of the growth of the ZnSe buffer layer, DM
While flowing Zn into the reaction tube 11, DIPS and DIPTe
Were alternately supplied to the reaction tube. At this time, the flow rate of DMZn is 5 μmol / min and the flow rate of DIPS is 80 μmol / min.
The flow rate of min and DIPTe is 15 μmol / min, and the supply time of DIPS and DIPTe is 35, respectively.
Seconds, 6 seconds, and each purge time was 5 seconds.

X was applied to the obtained ZnS-ZnTe superlattice.
As a result of line diffraction measurement, an X-ray satellite peak due to the superlattice structure was observed. It was found that the satellite peak intensity was about 5 times stronger on average than that of the sample manufactured in Example 1, and the periodicity of the superlattice structure was improved. One period of the superlattice structure obtained from the satellite peak is 17.4 A, which is 1 of the design value.
It was very close to 6.9A.

Although dimethyl zinc was used as a raw material for growing zinc in the above embodiment, the present invention is not limited to this, and diethyl zinc ((C ₂ H ₅ ) ₂ Zn) or dimethyl zinc / trimethylamine adduct is used as a raw material for zinc. ((CH ₃ )
Other raw materials such as ₂ Zn. (CH ₃ ) ₃ N)) may also be used.

In the above embodiment, Zn was used as the II-VI group compound semiconductor containing sulfur as one of the VI group constituent elements.
Although S was used, other mixed crystals such as MgZnS and BeZnS may be used, and ZnTe was used as the II-VI group compound semiconductor containing tellurium as one of the constituent elements of the VI group, but CdTe, ZnCdTe, etc. Other mixed crystals may be used. Moreover, the combination thereof is not limited. For example ZnS and C
dTe, ZnS and ZnCdTe, MgZnS and ZnT
e, MgZnS and CdTe, MgZnS and ZnCdT
e, BeZnS and ZnTe, BeZnS and CdTe, B
For example, eZnS and ZnCdTe may be used.

[0027]

As described above, ZnS-Z excellent in crystallinity while maintaining periodicity even in a film thickness of molecular layer order.
The nTe superlattice can be easily manufactured.

The superlattice obtained by the method of the invention is
It can be used for a blue-green semiconductor light emitting device and the like and is industrially useful.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of a growth apparatus used in the method of the present invention.

[Explanation of symbols]

 1a-1e Bubbler 11 Reaction tube 12 Substrate 13 High frequency coil

Claims (3)

(57) [Claims] 1. A II-VI group compound semiconductor containing sulfur (S) as one of the constituent elements of the VI group and tellurium (as one of the constituent elements of the VI group) using a metal organic chemical vapor deposition method. T
In the method e) to grow superlattices with Group II-VI compound semiconductor is contained, as a sulfur of the raw material, with diisopropyl sulfur _{((i-C 3 H 7} ) 2 S), diethyl tellurium as tellurium ingredients One of ((C ₂ H ₅ ) ₂ Te) and diisopropyl tellurium ((i-C ₃ H ₇ ) ₂ Te) is used. 2. The growth condition of the superlattice using the metalorganic vapor phase epitaxy method is that the pressure in the reaction tube is ⅕ or less of the atmospheric pressure. Production method. 3. The production of a semiconductor superlattice according to claim 1, wherein the II-VI group compound semiconductor constituting the semiconductor superlattice has a layer thickness of 10 molecular layers or less. Method.