JPH07201891A - Growth of ii-vi semiconductor crystal - Google Patents

Abstract

PURPOSE:To realize growth of II-VI semiconductor crystal without any unstability and mixture of impurity by using molecule which does not include hydrogen, has simple structure and weak biding force but is stable as the molecule as a dopant raw material gas but without using an accelerated electrons for dissociation. CONSTITUTION:In a method of causing a p-type ZnSe to grow on a GaAs substrate by the MBE process, a GaAs substrate introduced from a sample inlet 11 is attached to a substrate holder 12 installed within a growth chamber 10 kept under the ultra high vacuum condition of 10<-10>Torr or more and it is kept at the temperature of 350 deg.C. Growth of ZnSe is realized by heating solid raw material Zn (2) and Se (3). When two atom electron NSe (4), for example, is used, the N-doped p type ZnSe is grown by guiding the ZnSe gas compressed in a bomb 5 as the dopant gas to a gas cell 8 through a needle valve 6 and a flow meter 7 and then introducing the gas into an MBE growth chamber for irradiation to the GaAs substrate. Thereby the N-doped p-type ZnSe is grown. Hole concentration can be controlled precisely up to 10<16> to 10<19>cm<-3> depending on the flow rate of NSe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used in the electronics industry, particularly in the manufacture of semiconductor light emitting devices such as green-blue light emitting diodes and semiconductor lasers.

[0002]

2. Description of the Related Art Semiconductor lasers have characteristics such as small size, low power consumption and high reliability, and have various application fields such as communication and optical disks. Red color, ie wavelength 600nm
Long-wavelength lasers up to the band are AlGaInP, AlGaA
Crystals such as s and InGaAsP have been developed, and devices have already been put into practical use and mass-produced, making a great contribution to the industry. However, due to the technical difficulty in p-type doping of II-VI in the short wavelength range from green to blue, a laser device that can still be put to practical use has been developed, while a large potential demand is expected. It has not been.

Currently, the best p-type impurity doping method is the molecular beam epitaxy method (hereinafter referred to as MBE).
Method), an accelerated electron is made to collide with a nitrogen molecule (N ₂ ) to form atomic nitrogen, and then II-VI such as ZnSe.
This is a method of crystal growth while irradiating a growing surface of a group III semiconductor (for example, Extended Abstract of 1993 by MH Martin et al.
・ International Conference on Solid State Device and Material, Ex
tended Abstracts of the 1
993 International Confere
nce on Solid State Devices
and Materials, Makuhari,
1993, pp 56-58).

Further, in vapor phase growth and MBE, NH ₃ may be used as a dopant gas of N. In this case, H of NH ₃ is taken into the crystal to inactivate the N acceptor. There is a problem of "hydrogen passivation".

[0005]

The conventional method uses an electron acceleration mechanism by discharge or the like when forming N atoms, but it is very difficult to stably and precisely control the discharge state.
There is a problem in reproducibility, and a good low resistance p-type crystal has not been obtained yet. In addition, since this method uses electrons accelerated at high speed for the dissociation of N ₂ , extra impurity atoms generated on the wall surface of the dissociation device are taken into the crystal,
It reduces the luminous efficiency of the crystal and adversely affects the characteristics of the laser.

An object of the present invention is to provide a p-type II-VI group crystal growth method that does not rely on electron dissociation of N ₂ molecules that cause such instability and cause contamination of impurities. is there. The present invention also provides a p-type doping method that does not have the above-mentioned "hydrogen passivation" problem.

[0007]

The reason why a p-type II-VI semiconductor is unlikely to have a low resistance is that N ₂ used as a dopant gas has a strong N—N bond bonding force of 9.76 eV. Yes, it is difficult to be taken into the crystal. This dissociation energy of P ₂ and As ₂ is a raw material of group V element in the group III-V compound semiconductor MBE growth, such as InGaAsP, respectively 5.03EV,
It is well understood that it is 3.96 eV.

The present invention solves the above-mentioned problems of bond strength and hydrogen passivation by containing nitrogen and not hydrogen, having a simple structure, and having a bond strength far superior to that of N _2. On the other hand, it is characterized by using a molecule that is relatively stable as a dopant source gas and does not use accelerated electrons for its dissociation, but another characteristic is that the dopant gas is Except for some N, it means that it is composed of the VI group element of the II-VI crystal or its isoelectronic (isoelectronic) element.

Specifically, when considering the N doping to ZnSe, the dopant gas may be diatomic molecule NSe or the like. When NS or NTe is used, S or Te corresponds to the isoelectronic atom. Even if a small amount of isoelectronic atoms is introduced onto the group VI sublattice in the ZnSe crystal, it does not form a donor or a deep level because it belongs to the same group as Se, and has no adverse effect on the light emitting device. To satisfy these technical conditions, in the present invention, as a diatomic molecule of a dopant gas, NS, NSe, etc.
Examples are S ₂ and NSe ₂ . The binding energy of the molecule is 5.0 eV for NS and 4.0 e for NSe.
It is V, which is almost the same as that of P ₂ and As ₂ , and it is understood that they are easily dissociated. Further, by using these in the MBE method and the vapor phase epitaxy method, a low resistance p-type II
-Group VI crystals are obtained.

[0010]

EXAMPLES Examples of the present invention will be described below. The first example is MBE growth of p-type ZnSe on a GaAs substrate. FIG. 1 is a schematic diagram thereof. 10 ^-10 Tor
G introduced from the sample introduction port (11) into the substrate holder (12) installed in the ultra-high vacuum growth chamber (10) of r or more.
The aAs substrate is attached and kept at a temperature of 350 ° C. The growth of ZnSe is based on the solid raw materials Zn (2) and S.
e (3) is heated. The dopant gas is, for example, a gas (5) when using a diatomic molecule NSe (4).
The filled NSe gas is guided to the gas cell (8) through the needle valve (6) and the flow meter (7), introduced into the MBE growth chamber, and irradiated toward the GaAs substrate. By irradiating NSe gas at the same time as ZnSe growth, N-doped p-type ZnSe grows. The hole concentration is NSe
It is possible to precisely control from 10 ¹⁶ to 10 ¹⁹ cm ^-3 by the flow rate of.

The NSe gas may be NO, NS, NTe, or NO ₂ , NS ₂ , NSe ₂ , NTe ₂
May be This is because O, S, and Te are in the VI group and are isoelectronic elements, and therefore, even if mixed into ZnSe, there is no electrical adverse effect.

Group II-VI includes not only ZnSe but also
II-VI-VI type such as ZnSSe, or ZnM
It may be a II-II-VI-VI type crystal such as gSSe, or another type II-VI group mixed crystal, and is generally applied to the II-VI mixed crystal. In this way, II other than Zn and Se
In the case of containing a group or a group VI, a dedicated raw material cell for them may be added to the growth chamber. For example, when growing ZnSSe, the p-type dopant gas may be NSe. In this case, a mixed gas of NSe and NS may be used. In particular, for applications in which composition deviation due to the inclusion of a minute amount of Group VI element from the dopant gas poses a problem, NSe and NS
Are mixed at an appropriate ratio, the composition mixed with the VI group from the dopant gas is changed to S, Se of ZnS _x Se _1-x.
It is also possible to have the same composition.

Although the dopant gas used in the present invention is much easier to decompose than the conventional N ₂ gas, it is used at a high temperature (for example, 1200 ° C.) as a means for further promoting the decomposition.
It is also possible to provide a heater (9) which is heated to a temperature of about 1), bring this into contact with gas, and then irradiate the substrate.

To apply the present invention to a heterostructure laser device including a p-type II-VI group thin film as a part thereof, the present invention is applied only to the p-type II-VI group layer and other layers. For this, a conventional growth method may be applied.

To carry out the present invention in a vapor phase growth method, for example, to apply it to p-type ZnSe metalorganic vapor phase epitaxy method, using dimethyl zinc as a source gas of Zn and dimethyl selenium as a source gas of Se, a growth temperature is increased. For example, hydrogen gas is used as a carrier on a GaAs substrate crystal installed on a carbon susceptor heated to 350 ° C. together with these gases, and N
A dopant gas such as Se or NS is flown. As a result, low resistance p-type ZnSe is obtained. At this time, hydrogen as a carrier gas does not cause the above-mentioned hydrogen passivation phenomenon, and the dopant gas is also NH ₃ which has been conventionally used.
Different from nitrogen compound gas containing hydrogen, such as
Since hydrogen passivation does not occur, efficient p
Type doping is possible. The present invention can also be implemented by other vapor phase growth methods such as the chloride VPE method and the hydride VPE method.

The doping gas used in the present invention is diluted with a diluting gas such as a rare gas such as Ar or He and stored in a cylinder, and is stored in the MBE growth chamber or the metal organic chemical vapor deposition as it is at the time of use. It is also possible to introduce it into the reaction tube at times.

[0017]

By applying the present invention, a low-resistance p-type II-VI group semiconductor, which has hitherto been impossible, can be easily obtained, and it is no longer necessary to dissociate gas by means such as discharge. The accuracy of controlling the impurity concentration is significantly improved. As a result, a voltage-current characteristic with a rising voltage of 4 V or less can be obtained. Further, the concentration of impurities other than the dopant is reduced, and the luminous efficiency is significantly improved. This result can be immediately applied to the II-VI group heterostructure semiconductor laser, and a large reduction in series resistance and a reduction in oscillation threshold can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining MBE growth of low resistance N-doped p-type ZnSe.

[Explanation of symbols]

 1 GaAs Substrate Crystal 2 Solid Zn and Cell for II-VI Group Crystal Growth 3 Solid Se and Cell for II-VI Group Crystal Growth 4 Cylinder 6 Dopant 2 Atom Molecular Gas NSe 5 NSe Accommodating Needle 6 Flow Rate Adjusting Needle Valve 7 Flow meter 8 Gas cell for dopant gas 9 Heater 10 MBE growth chamber 11 Sample introduction port 12 Substrate holder 13 Growth chamber exhaust holder

Claims (6)

[Claims] 1. In the growth of a II-VI group binary or multi-element mixed crystal semiconductor by a molecular beam epitaxy method or a vapor phase epitaxy method, a 2 to 3 atomic molecular gas consisting of a group V and a group VI is used as a p-type dopant material. A method for growing a p-type II-VI group semiconductor crystal, comprising: 2. The diatomic molecule dopant gas is NO, N
One kind of gas among S, NSe, and NTe, or
The p-type II-VI group semiconductor crystal growth method according to claim 1, wherein the mixed gas is composed of a plurality of types. 3. The triatomic molecule dopant gas is NO ₂ ,
One kind of gas among NS ₂ , NSe ₂ and NTe ₂ ,
Or multiple types of gas, or NO and N with them
The method for growing a p-type II-VI group semiconductor crystal according to claim 1, wherein the mixed gas is S, NSe, or NTe. 4. The group II element of the group II-VI element is Zn,
The p-type II-V according to claim 1, wherein the p-type II-V is composed of one or more of Cd, Mg and Mn, and the group VI element is composed of one or more of S, Se and Te.
Group I semiconductor crystal growth method. 5. V of a 2 to 3 atomic molecule dopant gas
The p-type II- according to claim 1 or claim 2 or claim 3 or claim 4, wherein the group I element corresponds to all or part of the group VI element of the group II-VI semiconductor.
Group VI semiconductor crystal growth method. 6. The method according to claim 1, wherein the dopant gas is thermally dissociated, and then the growth surface is irradiated to perform doping. Method for growing p-type II-VI semiconductor crystal.