JP2942827B1 - Method for manufacturing n-type ZnTe semiconductor - Google Patents

Abstract

An object of the present invention is to provide a method capable of producing a low-resistivity n-type ZnTe semiconductor with good reproducibility, and to provide a low-resistivity n-type ZnTe semiconductor.
Ohmic contact with the type ZnTe semiconductor provides a good electrode material. SOLUTION: A Zn source gas, a Te source gas, and an Al doping gas or Cl are formed by metal organic chemical vapor deposition.
In a method for producing an n-type ZnTe semiconductor on a substrate by reacting a doping gas, the molar ratio of Zn and Te in the source gas is Te / Zn ≧ 1.1 or Te / Zn.
A method for producing an n-type ZnTe semiconductor, characterized in that the source gas is supplied so that /Zn≦0.9. Further, a W electrode or an In alloy electrode containing Hg,
By forming on the n-type ZnTe semiconductor, an n-type ZnTe semiconductor element having excellent ohmic contact can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an n-type ZnTe semiconductor and an n-type ZnTe semiconductor device, and more particularly, to an n-type ZnTe semiconductor having a low resistivity and suitable for use in various semiconductor devices such as light-emitting devices. The present invention relates to a method for manufacturing a ZnTe semiconductor and an n-type ZnTe semiconductor device.

[0002]

2. Description of the Related Art ZnTe is approximately 2.3 eV at room temperature.
It is a direct transition type II-VI compound semiconductor having a band gap of, and is expected to be applied as a light emitting element such as a high luminance green light emitting element, a light receiving element, and a solar cell.
Further, since ZnTe has a large atomic number of constituent elements, XTe
It is also expected to be applied as an optical waveguide device such as a light detection device such as a line or a light modulation device using a high Pockels coefficient.

[0003] It is difficult to control the conduction type of a ZnTe semiconductor due to the self-compensation effect and the action of residual impurities. Was obtained only. As a result, it was difficult to manufacture the device using only the ZnTe semiconductor. However, in recent years, metal organic chemical vapor deposition (MOCVD)
Research on n-type doping under non-thermal equilibrium conditions, such as molecular beam epitaxy and laser doping, has been actively conducted in various research institutions.

"Applied Physics, Vol. 49, No. 5" (198
0), p. 452-459, discloses a method of immersing a ZnTe crystal in a Zn melt containing Al and thermally diffusing Al into the crystal to obtain an n-type ZnTe semiconductor. In addition, "Semicond. Sci. Tech
nol. 6 "(1991), pages A105-108,
Diisopropyl tellurium (DiPTe) and diethylzinc (DEZn) were used as source gases, and ethyl iodide (EtI) was used as a doping gas.
A method of manufacturing an In-doped n-type ZnTe semiconductor on a ZnTe substrate by an OCVD method is disclosed.

[0005] "Jpn. J. Appl. Phys. Vo
l. 33 "(1994), pages 980-982, dimethylzinc (DMZn) and diethyltellurium (DETe).
Is used as a source gas, and triethylaluminum (TEAl) is used as a doping gas.
A method of manufacturing an Al-doped n-type ZnTe semiconductor on a (100) ZnTe substrate by a VD method is disclosed. "Materials Science F"
orum Vols. 182 to 184 ”(1995), pp. 353 to 358, show that A on a p-type ZnTe semiconductor
There is disclosed a method of manufacturing an Al-doped n-type ZnTe semiconductor by depositing an l layer and then irradiating the Al layer with a laser to diffuse Al into the ZnTe semiconductor.

[0006]

However, in any of the above-mentioned methods, the n-type ZnTe semiconductor has only a high resistivity of about 10 ⁵ Ωcm at present. On the other hand, “Jpn.J.
Appl. Phys. Vol. 33 ", an n-type ZnT having a low resistivity of several Ωcm
Although an e-semiconductor can be obtained, its reproducibility is poor, and at present, an n-type ZnTe semiconductor with low resistivity cannot be stably obtained.

The present invention provides a method for producing a low resistivity n-type ZnTe semiconductor with good reproducibility, and provides an electrode material having good ohmic contact with the low resistivity n-type ZnTe semiconductor. Aim.

[0008]

According to the present invention, a Zn source gas, a Te source gas, and an A
l doping gas to react, n-type ZnTe
In the method of manufacturing a semiconductor, the source gas is supplied such that a molar ratio of Zn and Te in the source gas satisfies Te / Zn ≧ 1.1. It is a manufacturing method.

Further, the present invention provides a method for producing an n-type ZnTe semiconductor by reacting a Zn source gas, a Te source gas, and a Cl doping gas by a metal organic chemical vapor deposition method. A method for producing an n-type ZnTe semiconductor, characterized in that the source gas is supplied such that the molar ratio of Te and Zn satisfies Te / Zn ≦ 0.9.

When manufacturing an n-type ZnTe semiconductor by doping Al or Cl by MOCVD, Zn
By setting the molar ratio between the source gas and the Te source gas as described above, an extremely large amount of Al or Cl can be doped with stability.

Since Al enters the crystal by substituting for Zn atoms, Zn vacancies are easily generated by setting Te / Zn ≧ 1.1. Therefore, Al atoms can easily enter this position. it can. As a result, Al is stably incorporated into the crystal under the above conditions, and the donor becomes a shallow donor. On the other hand, Cl substitutes for Te atoms and enters the crystal, so that Zn / Te ≦
By setting the ratio to 0.9, Te vacancies are easily generated, so that Cl atoms can easily enter this position.
As a result, Cl is stably incorporated into the crystal under the above conditions, and a shallow acceptor is obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail in embodiments of the present invention. In the manufacturing method of the present invention when an Al doping gas is used, the lower limit of the molar ratio of Te and Zn in the source gas of the ZnTe semiconductor is 1.1.
And it is preferably 2, and more preferably 3. If the lower limit is smaller than 1.1, the object of the present invention cannot be achieved.

The upper limit of the molar ratio between Te and Zn in the source gas is not particularly limited, but the amount of generated Zn vacancies is larger than the amount of Al atoms taken into the crystal. It is preferably 10 and more preferably 5 because the possibility that a complex of Zn vacancy and Al is easily formed and the compensation effect by these makes it difficult to control the n-type.

In the manufacturing method of the present invention when a Cl doping gas is used, the upper limit of the molar ratio between Te and Zn in the source gas of the ZnTe semiconductor needs to be 0.9, preferably 0. .5, more preferably 0.3
It is. If the upper limit is larger than 0.9, the object of the present invention cannot be achieved.

The lower limit of the molar ratio between Te and Z in the raw material gas is not particularly limited, but a complex with Te vacancies and Cl is likely to be formed, which causes a deep energy level. Free carriers are reduced to form n
Since it is difficult to control the shape, it is preferably 0.1, and more preferably 0.2.

The Zn source gas that can be used in the present invention contains Zn and is formed by MOCVD.
Although it is not particularly limited as long as it forms Te, dimethyl zinc (DMZn), diethyl zinc (D
EZn), and dimethylzinc triethylamine (DMZ)
n-TEN) and the like. Further, Te source gas that can be used in the present invention is Te source gas.
Is not particularly limited as long as ZnTe is formed by MOCVD, and diethyl tellurium (DETe), diallyl tellurium (DATe),
And diisopropyl tellurium (DiPTe).

When the above-described gases are used as the source gases, the molar ratio of Zn to Te in each source gas corresponds to the molar ratio of the source gases used. If the Al doping gas contains Al, is decomposed by the MOCVD method, is taken in as an Al donor in the ZnTe semiconductor, and reverses the conduction type of the ZnTe semiconductor to form an n-type ZnTe semiconductor, Although not particularly limited, triethyl aluminum (TEA)
l), trimethylaluminum (TMAl), and dimethyl aluminum hydride (Deal), triisobutylaluminum (i-Bu ₃ Al) and the like can be exemplified. Similar to the Al doping gas, examples of the Cl doping gas include organometallic compounds such as zinc chloride (ZnCl ₂ ) and ethyl chloride (EtCl).

From the standpoint of improving the reaction efficiency by efficiently decomposing the source gas and the doping gas and shortening the reaction time, it is preferable that the temperature of the substrate used is higher. On the other hand, if the substrate temperature becomes too high, Z
The vacancy concentration at the n-site increases, and the vacancy and an Al or Cl donor form a complex, which reduces the effective amount of the donor in the ZnTe semiconductor to obtain a ZnTe semiconductor with low resistivity. Can not do.

Therefore, in the manufacturing method of the present invention using an Al doping gas, the substrate temperature is 20
0 to 400 ° C., and more preferably 340 to 400 ° C.
Preferably it is 380 ° C. Similarly, in the manufacturing method of the present invention using a Cl doping gas, the substrate temperature is preferably from 200 to 400 ° C, and more preferably from 340 to 380 ° C.

As a substrate that can be used in the manufacturing method of the present invention, a GaAs substrate, a silicon substrate, a sapphire substrate, a silicon carbide substrate and the like can be used in addition to a ZnTe substrate.

In the manufacturing method of the present invention, it is necessary to manufacture a ZnTe semiconductor by MOCVD. FIG.
FIG. 1 shows an example of an MOCVD apparatus for implementing the manufacturing method of the present invention. MOCVD apparatus 2 shown in FIG.
Reference numeral 0 denotes a stainless steel chamber 1 which has been subjected to an inner wall treatment so that an ultra-high vacuum can be achieved.
And a pedestal 3 coated with SiC for supporting the source gas, and guides the source gas and the doping gas directly above the substrate 2.
Further, a resistance type heater 4 is embedded in the pedestal 3 to heat the substrate 2, and the temperature of the substrate 1 is controlled by controlling the current of the heater. Further, M
Cooling water can be supplied to the chamber wall of the OCVD apparatus 20 through the cooling water inlet 5 and the cooling water outlet 6 in order to prevent the chamber wall from being unnecessarily heated by the substrate heating. Above the MOCVD apparatus 20, gas inlets 7 and 8 for introducing a source gas and a doping gas are provided.

Although not shown in FIG. 1, the source gas and the doping gas directly above the pedestal 3 may be separately introduced or a new inner tube may be provided so as to mix them. Further, the substrate can be heated by a high-frequency heating coil or infrared rays instead of the embedded resistance heater. Further, the present apparatus is of a vertical type in which gas flows vertically, but may be a horizontal type in which gas flows horizontally.

The source gas containing Zn is hydrogen (H ₂ )
The carrier gas is introduced into the MOCVD apparatus 20 from the gas inlet 7. On the other hand, a source gas containing Te and a doping gas are introduced into the MOCVD apparatus 20 from the gas inlet 8 together with the carrier gas so that the molar ratio between Zn and Te in the source gas falls within the above range.
Next, the substrate 1 is heated to the substrate temperature by passing a current through the heater 4. The temperature of the substrate 1 is controlled by a thermocouple 9. The gas pressure during the reaction is
The pressure is maintained at 1 to 900 torr by evacuating from a vacuum pump (not shown).

By the above operation, the reaction is carried out for 1 to 3
N-type Zn having a thickness of 1 to 10 μm
A Te semiconductor is manufactured. As described above, the n-type ZnTe semiconductor obtained according to the manufacturing method of the present invention is 0.1 to 1
It shows a very low resistivity of 0 Ωcm.

On the other hand, in the case of forming an element made of the semiconductor, in order to form an ohmic contact at a contact interface and obtain a linear current-voltage characteristic, it is necessary to use a W electrode or an H electrode.
It is necessary to form an In alloy electrode containing g. Al and A conventionally used as electrode materials
When an electrode made of a material such as u is formed on the n-type ZnTe semiconductor, a Schottky barrier is formed at the contact interface, and an ohmic contact cannot be obtained.

In the In alloy, Hg can exist in a uniformly dispersed state, or can exist with a predetermined concentration distribution. Hg in the In alloy
The content of is not particularly limited, but is preferably 0.1 to 10 mol%, and more preferably 0.2 to 5 mol%.

The electrode can be formed by using a sputtering method, a vacuum evaporation method, an electron beam evaporation method, a plating method, or the like. In the case of a W electrode, as described below, the sputtering method is used. This is preferably performed, and in the case of an In alloy electrode, it is preferably performed using a vacuum evaporation method.

First, the W electrode is formed by n-type ZnTe.
A semiconductor is placed in a chamber, and the inside of the chamber is 10 ⁻⁷ t.
After evacuating the pressure to not more than orr, the pressure in the chamber was set to 1 × 10 ^{−2 to} 5 × 10 ⁻² torr by introducing an argon gas, and then the n-type ZnTe semiconductor was subjected to RF reverse sputtering. Clean the surface. Then, an RF of 0.64 to 1.9 W / cm ² is applied to the W target.
By performing sputtering, a W film having a thickness of 0.2 to 1 μm is formed on the surface of the n-type ZnTe semiconductor. Then, preferably, in a reducing atmosphere such as H ₂ gas, 280 to
Heat treatment is performed at 320 ° C. for 3 to 5 minutes. By this heat treatment, the electrodes formed on the n-type ZnTe semiconductor
Ohmic contact can be easily obtained.

In the In alloy electrode, the n-type ZnTe semiconductor is put into a chamber, and the inside of the chamber is evacuated to 10 ^-6 torr or less. Then, the In-Hg alloy is heated and evaporated to a thickness of 0.2 to 1 μm. Formed. Thereafter, heat treatment is preferably performed at 250 to 310 ° C. for 3 to 5 minutes, so that an electrode having an ohmic contact can be easily formed.

Since the n-type ZnTe semiconductor device obtained in this manner can have the low resistivity as described above, the n-type ZnTe semiconductor device and the conventional p-type ZnTe semiconductor device can be obtained.
By forming a PN junction with a type ZnTe semiconductor element, it is possible to manufacture a light-emitting element such as a green light-emitting element, a light-receiving element, and various devices such as a solar cell and a light modulation element from only a conventional ZnTe semiconductor. Can be.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. Examples 1 to 3 and Comparative Examples 1 and 2 A ZnTe single crystal substrate was used as the substrate 1, and the M shown in FIG.
Using an OCVD apparatus, ZnTe was
Semiconductors were manufactured. After placing the substrate 1 on the pedestal 2, H ₂ gas was introduced into the MOCVD apparatus 20 from the gas inlet 7 and the substrate temperature was heated to about 450 ° C. to remove the natural oxide film on the substrate 1.

Then, after setting the temperature of the substrate 1 to about 380 ° C., DMZn and DETE were mixed with the H ₂ carrier gas together with the H ₂ carrier gas at the gas inlets 7 and 8 so that the molar flow ratio became as shown in Table 1. While introducing it into the MOCVD apparatus 20 and adding TEAl to the DMZn gas at 1 mol%.
And the MOCVD apparatus 2
0 and reacted for 3 hours to produce a ZnTe semiconductor having a thickness of about 7 to 10 μm.

The conductivity type and resistivity of the obtained ZnTe semiconductor were determined by Van der Pau.
w) Evaluated by a measuring method. In addition, the obtained ZnTe
In order to evaluate the reproducibility of the semiconductor, the above experiment was performed four times, and the standard deviation of the resistivity of the ZnTe semiconductor obtained each time was obtained. Note that the resistivity is an average value of the ZnTe semiconductor obtained in the four experiments. Table 1 shows the results.

[0034]

[Table 1]

Examples 4 to 6 and Comparative Examples 3 and 4 As the MOCVD apparatus and the substrate 1, the apparatus shown in FIG. 1 and the ZnTe single crystal substrate were used as described above. After the natural oxide film on the substrate 1 is removed by the above-described procedure, the DMZn is removed.
And DETE such that the molar flow ratio is as shown in Table 2,
Along with the H ₂ carrier gas, M
While being introduced into the OCVD apparatus 20, ZnCl ₂ was adjusted to 1 mol% with respect to the DETe gas,
The gas is introduced into the MOCVD apparatus 20 through the gas inlet 7 and 3
After reacting for a time, a ZnTe semiconductor having a thickness of about 7 to 10 μm was manufactured.

The conductivity type and resistivity of the obtained ZnTe semiconductor were determined in the same manner as in the above Examples and Comparative Examples, and the reproducibility of the ZnTe semiconductor was evaluated by determining the standard deviation in the same manner. Table 2 shows the results
Shown in

[0037]

[Table 2]

As is clear from Tables 1 and 2, the ZnTe semiconductors manufactured by the method of the present invention all show n-type conductivity, exhibit an extremely low resistivity of about 0.1 to 10 Ωcm, and It can be seen that the reproducibility is extremely high.

Example 7 A W electrode was formed on the n-type ZnTe semiconductor obtained in Example 1 according to the procedure described in "Embodiment of the Invention" as follows. The above-mentioned n-type ZnTe semiconductor is put into a chamber of a sputtering apparatus, and 10 ⁻⁷ t
After evacuating to orr or lower, Ar was introduced to maintain the pressure in the chamber at 1.5 × 10 ^-2 torr. Next, RF power of 1.3 W / cm ² was applied to the W target to form a 1 μm W film on the n-type ZnTe semiconductor.
Then, after introducing H ₂ gas into the chamber, the n-type ZnTe semiconductor is heated to 300 ° C. and treated for 3 minutes.
Annealing of the W film was performed.

A terminal was attached to the electrode of the n-type ZnTe semiconductor device manufactured as described above, and the current-voltage characteristics were examined with a semiconductor parameter analyzer. FIG. 2 is a diagram showing current-voltage characteristics of an n-type ZnTe semiconductor device manufactured according to this example. As apparent from FIG. 2, the W electrode formed according to the present embodiment has 280 to 280 electrodes.
It was found that in the temperature range of 320 ° C., the n-type ZnTe semiconductor exhibited excellent ohmic contact properties and exhibited linear current-voltage characteristics.

Comparative Example 5 The n-type ZnTe semiconductor obtained in Example 1 was put into a chamber of a sputtering apparatus, evacuated to 10 ⁻⁷ torr or less, and then Ar was introduced to reduce the pressure in the chamber to 1.5 × 10 5.
^-2 torr. Next, 1.
By applying RF power of 3 W / cm ² , the n-type ZnTe
An Al film of 1 μm was formed on the semiconductor. Then, after introducing H ₂ gas into the chamber, the n-type ZnTe semiconductor was heated to 340 ° C., and a heat treatment was performed for 3 minutes to perform an annealing process on the Al film.

Terminals were attached to the electrodes of the n-type ZnTe semiconductor device manufactured as described above, and the current-voltage characteristics were examined using a semiconductor parameter analyzer. FIG. 3 is a diagram showing current-voltage characteristics of an n-type ZnTe semiconductor device manufactured according to this comparative example. As is clear from FIG. 3, the electrode made of Al formed according to the present comparative example cannot obtain ohmic contact with the n-type ZnTe semiconductor and has a non-linear current-voltage characteristic in which only a small amount of current flows. Was found.

[0043]

As described above, according to the manufacturing method of the present invention, an n-type ZnTe semiconductor having a low resistivity can be obtained with good reproducibility, and an excellent ohmic contact with this n-type ZnTe semiconductor can be obtained. An electrode exhibiting properties can be provided. Therefore, it is possible to provide an n-type ZnTe semiconductor device having extremely low resistivity, and as a result,
Various devices such as a light-emitting element, a light-receiving element, a solar cell, and an optical waveguide element can be manufactured from only a ZnTe semiconductor, which has been conventionally difficult.

[Brief description of the drawings]

FIG. 1 shows MOCVD for implementing the manufacturing method of the present invention.
1 shows an example of an apparatus.

FIG. 2 is a diagram showing current-voltage characteristics of an n-type ZnTe semiconductor device manufactured according to the manufacturing method of the present invention.

FIG. 3 shows n produced according to a method different from the present invention.
FIG. 3 is a diagram showing current-voltage characteristics of a type ZnTe semiconductor element.

[Explanation of symbols]

 Reference Signs List 1 chamber 2 substrate 3 pedestal 4 heater 5 cooling water inlet 6 cooling water outlet 7, 8 gas inlet 9 thermocouple 10 exhaust outlet 20 MOCVD apparatus

Claims (13)

(57) [Claims] 1. A method for producing an n-type ZnTe semiconductor on a substrate by reacting a Zn source gas, a Te source gas, and an Al doping gas by a metalorganic chemical vapor deposition method, comprising: And the molar ratio of Te to Te
A method for producing an n-type ZnTe semiconductor, wherein the source gas is supplied so that /Zn≧1.1. 2. The method according to claim 1, wherein the source gas is supplied such that the molar ratio of Zn and Te in the source gas satisfies 10 ≧ Te / Zn ≧ 1.1. Of manufacturing an n-type ZnTe semiconductor. 3. The temperature of the substrate during the reaction is 20
The temperature is from 0 to 400 ° C.
3. The method for producing an n-type ZnTe semiconductor according to item 1. 4. A method for producing an n-type ZnTe semiconductor by reacting a Zn source gas, a Te source gas, and a Cl doping gas by a metalorganic vapor phase epitaxy method, wherein Zn and Te occupying the source gas are mixed. When the molar ratio is Te
A method for producing an n-type ZnTe semiconductor, wherein the source gas is supplied so that /Zn≦0.9. 5. The raw material gas is supplied such that the molar ratio of Zn and Te in the raw material gas satisfies 0.9 ≧ Te / Zn ≧ 0.1. 3. The method for producing an n-type ZnTe semiconductor according to item 1. 6. The temperature of the substrate during the reaction is 20
The temperature is 0 to 400 ° C.
3. The method for producing an n-type ZnTe semiconductor according to item 1. 7. An n-type ZnTe semiconductor manufactured by the method for manufacturing an n-type ZnTe semiconductor according to any one of claims 1 to 6. 8. An n-type ZnTe semiconductor device, wherein a W electrode or an In alloy electrode containing Hg is formed on the n-type ZnTe semiconductor according to claim 7. 9. An n-type ZnTe semiconductor according to claim 7, wherein after forming a W electrode or an In alloy electrode containing Hg, annealing is performed in a reducing atmosphere. A method for manufacturing a ZnTe semiconductor device. 10. A light-emitting element, wherein the n-type ZnTe semiconductor element according to claim 8 and a p-type ZnTe semiconductor element have a PN junction. 11. A light receiving element, wherein the n-type ZnTe semiconductor element according to claim 8 and a p-type ZnTe semiconductor element are formed by PN junction. 12. A solar cell, wherein the n-type ZnTe semiconductor element according to claim 8 and a p-type ZnTe semiconductor element are formed by a PN junction. 13. An optical waveguide device, wherein the n-type ZnTe semiconductor device according to claim 8 and a p-type ZnTe semiconductor device are formed by PN junction.