JP2003137700A - ZnTe-BASED COMPOUND SEMICONDUCTOR SINGLE CRYSTAL AND SEMICONDUCTOR DEVICE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ZnTe-based compound semiconductor single crystal having a low detect density and containing a carrier in a high concentration, which is effective for obtaining a semiconductor device having excellent light emitting properties, and to provide the semiconductor device having the ZnTe- based compound semiconductor as a base body. SOLUTION: The ZnTe-based compound semiconductor single crystal is formed by doping a dopant element characterized in that the dopant element can occupy a Zn lattice position, and the energy at the time the dopant element occupies the Zn lattice position is stabler than the energy when a vacancy is formed at the Zn lattice position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ZnTe compound semiconductor single crystal having a low defect density suitable for a material of a semiconductor device and a semiconductor device having the same as a substrate.

[0002]

2. Description of the Related Art At present, a II-VI group compound semiconductor single crystal is expected as a material that can be used for a blue or green light emitting element such as a light emitting diode.

For example, a pn junction type diode is manufactured by using a ZnSe based compound semiconductor single crystal in which a number of layers of ZnSe based mixed crystal thin films are grown on a GaAs substrate by a molecular beam epitaxial growth method. In this case, ZnS
Since it is considered difficult to control a p-type semiconductor in a thermal equilibrium state, an e-based compound semiconductor single crystal is formed using a special device called a radical particle beam source.

[0004]

However, the p-type ZnSe-based compound semiconductor single crystal obtained by the above method has a low dopant activation rate (the rate at which the doped dopant is effectively activated as a carrier), and emits light. The crystal did not have a low resistance enough to be used as a device. In addition, as the dopant is introduced into the crystal, defects that inhibit the activation of the dopant are also introduced into the crystal at the same time.
The crystallinity deteriorated due to these defects. For this reason, it has been difficult to manufacture a highly reliable light emitting diode using a p-type ZnSe-based compound semiconductor single crystal.

On the other hand, a p-type semiconductor single crystal using a ZnTe-based material can be relatively easily manufactured without using a special device. However, since it is difficult to control defects as in the case of ZnSe-based compound semiconductor single crystal, a highly reliable light emitting device using a p-type ZnTe-based compound semiconductor single crystal has not been developed.

The present invention is effective for obtaining a semiconductor device having good light emission characteristics, and has a small defect density and a high carrier concentration Z.
An object of the present invention is to provide an nTe-based compound semiconductor single crystal and a semiconductor device having the ZnTe-based compound semiconductor as a base.

[0007]

The present invention has been made to achieve the above object, and is an element occupying a Zn lattice position, and the energy at the time of occupying the Zn lattice position is Z.
It is a ZnTe-based compound semiconductor single crystal doped with a first dopant element, which is more stable than the energy when vacancies are formed at the n-lattice position. That is, it is a ZnTe-based compound semiconductor single crystal in which the constituent element of the first dopant occupies the Zn lattice position and is more energetically stabilized than in the case where the vacancy exists at the Zn lattice position.

Specifically, a group 1 (1A) element or a group 11 (1B) element is suitable as the first dopant, and for example, at least one of Ag, Cu, Li, and Na is ZnTe. The compound semiconductor single crystal may be doped. However, since it is practically difficult to dope Li and Na into the crystal with high purity, Ag and Cu are suitable as the first dopant, and Ag is more suitable in terms of energy.

The ZnTe-based compound means the 12th (2
It means that the compound is a II-VI group compound containing at least Zn and a 16 (6B) group element of the B) group element, and easily causing Zn vacancy defects.

Further, by simultaneously doping the first dopant and a second dopant that occupies the Te lattice position and controls the conductivity type to p-type, a p-type ZnTe system having excellent crystallinity is obtained. A compound semiconductor can be manufactured. For example, it is desirable that the second dopant contains at least one of N, P, and As that occupies the Te lattice position.

The p-type ZnTe compound semiconductor thus produced has a p-type carrier concentration of 1 × 10 ¹⁸ cm 2.
^-3 or more and carrier mobility is 40 cm ² / V · s
ec or more and the resistance is 0.1 Ω · m or less.

On the other hand, by simultaneously doping the first dopant and the third dopant composed of an element for controlling the conductivity type to n-type, an n-type Z having excellent crystallinity is obtained.
An nTe compound semiconductor can be manufactured. In this case, for example, the third dopant is Al, Ga, I
It is desirable to contain at least one of n and Cl. However, it is necessary to make the third dopant concentration higher than the first dopant concentration.

The n-type ZnTe compound semiconductor thus produced has an n-type carrier concentration of 1 × 10 ¹⁸ cm 2.
^-3 or more and carrier mobility is 130 cm ² / V ·
It is not less than sec and the resistance is not more than 0.05 Ω · m.

As described above, by doping the ZnTe compound semiconductor single crystal with an element occupying the Zn lattice position such as Ag or Cu as the first dopant, Zn
It is possible to suppress the occurrence of the vacancy defect of 1 and obtain a ZnTe compound semiconductor single crystal having a low vacancy defect density and a low composite defect density due to Zn vacancy. Therefore,
Since the obtained ZnTe-based compound semiconductor single crystal has very good crystallinity, it is possible to manufacture a highly reliable light emitting element, and it is expected that the life of the semiconductor device can be extended.

ZnTe-based compound semiconductors to which this method is effective include ZnTe, ZnMgTe, and ZnMnT.
e, ZnCdTe, ZnBeTe, ZnMgSeTe,
Examples include ZnBeMgTe and ZnCdSeTe.

The present invention is not limited to the ZnTe-based compound semiconductor single crystal, but is also effective for the CdTe-based compound semiconductor single crystal and the BeTe-based compound semiconductor single crystal, and is doped with Ag or Cu as the first dopant. By doing so, it is possible to effectively suppress the occurrence of defects due to Cd holes or Be holes.

These ZnTe-based compound semiconductor single crystals can be obtained by a bulk crystal growth method such as Bridgman method or vertical cooling method (VGF method), or a molecular beam epitaxy (MBE) method on a ZnTe substrate. , Or chemical vapor deposition (CVD method: Chemical Vaper Dep
osition), especially metal organic chemical vapor deposition (MOCVD: Met
a-organic Chemical Vaper Deposition) method.

The details of the present invention will be specifically described below. Conventionally, when a p-type ZnTe compound semiconductor single crystal is produced, the 15th P, As, N, etc. that enter the Te lattice position
By using a group (5B) element as a p-type dopant,
It was common to dope the crystal with only the type dopant. Further, in order to obtain a semiconductor single crystal having a high carrier concentration, a method of increasing the doping amount of the p-type dopant is adopted. For example, a special device called a radical particle beam source is used for activation by the MBE method. A large amount of the converted N (p-type dopant) is doped.

However, since N occupying the Te lattice position is not so stable in terms of energy, there arises a problem that the defect density in the crystal increases. Then, the reliability of the light emitting device based on such ZnTe compound semiconductor crystal is adversely affected.

As described above, according to the conventional method, the p-type Z having a high carrier concentration without increasing the crystal defect density is obtained.
It is difficult to produce an nTe compound semiconductor single crystal, and if a high carrier concentration is pursued, the crystal defect density increases, and a satisfactory p-type ZnTe compound semiconductor cannot be obtained.

Therefore, as a result of research on doping, the present inventors have found from theoretical calculation that ZnTe compound semiconductors are energetically stabilized when Zn lattice positions become vacancies. Furthermore, Zn and Te
It has been found that Zn vacancies are relatively easily diffused between the lattices due to the low binding energy of, and complex defects are likely to be generated due to the diffusion of vacancies.

That is, the p-type ZnTe compound semiconductor is p-type
A group 15 (5B) element as a type dopant occupies the Te lattice position, Zn vacancies are generated, and a complex defect is generated due to the generation of Zn vacancies, so that the crystal defect density is increased and crystals are formed. It turned out that the sex is reduced.

Therefore, the present inventors set the Zn lattice position to Z
It was considered that the density of Zn vacancies can be reduced by occupying an element that is more energetically stable than the energy for forming n vacancies. Then, p consisting of a Group 15 (5B) element
An experiment was conducted in which, in addition to the type dopant, an element occupying the Zn lattice position was injected as a dopant, and it was found that the element was stabilized while occupying the Zn lattice position, and the density of Zn vacancies could be reduced. It was also confirmed that the reduction of the density of Zn vacancies suppressed the generation of compound defects due to Zn vacancies, and the crystal defect density was reduced.

Here, Ag, Cu or the like is suitable as an element that occupies a Zn lattice position that is more stable than the energy that forms the Zn vacancy, and Zn vacancy is obtained by doping this element as one of the dopants. It has been clarified that the defects caused by can be effectively suppressed.

As described above, a large amount of N is doped by simultaneously doping at least one element of Ag or Cu, which is an element occupying the Zn lattice position, with a dopant such as nitrogen (N) for controlling the conductivity type. Since it is possible to suppress the generation of Zn vacancies, it is possible to prevent adverse effects due to defects caused by Zn vacancies and obtain a semiconductor single crystal having a high carrier concentration.

It was also confirmed that Ag has a slightly higher activation energy as a p-type dopant, and therefore works effectively as a p-type dopant. That is, as compared with the case where only N, As, and P are implanted as the p-type dopant, the case where the p-type dopant is doped with Ag at the same time has a higher carrier concentration and a smaller number of defects in the p-type ZnTe semiconductor single crystal. was gotten.

When an n-type ZnTe compound semiconductor is produced, Al, Ga, In, Cl are used as n-type dopants.
N-type ZnT having a high carrier concentration and few defects by simultaneously doping Ag or Cu with a lower concentration than the n-type dopant.
It was also confirmed that an e semiconductor single crystal was obtained.

The present invention has been completed based on the above findings, and when a ZnTe compound semiconductor single crystal is produced,
An element occupying a Zn lattice position such as Ag or Cu is doped at the same time as a dopant for controlling the conductivity type, thereby suppressing the generation of Zn vacancies and Zn having a low defect density.
A Te compound semiconductor single crystal is obtained.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION This embodiment is an example of a light emitting diode as a semiconductor element according to the present invention, and is a p-type Z
ZnTe in which each layer is epitaxially grown on the nTe substrate by the MBE method to form a single hetero pn junction.
It is an example of a light emitting diode based on a compound semiconductor.

Note that Ag and N were used as dopants for the p-type ZnTe compound semiconductor layer, and Al and Ag were used as dopants for the n-type ZnTe compound semiconductor layer.

First, on a p-type ZnTe substrate, Ag and N were doped so that the carrier concentration was 1 × 10 ¹⁸ cm ⁻³ to form a p-type ZnTe buffer layer of 2.0 μm. At this time, high-purity Zn metal is used as a Zn source which is a semiconductor raw material, high-purity Te metal is used as a Te source, high-purity Ag metal is used as an Ag dopant, and radical activated nitrogen is used as a nitrogen source. I was there.

Next, on the p-type ZnTe buffer layer,
Carrier concentration of 1 × ¹⁰ 17 cm ^{- 3} become as Ag
A ZnTe active layer doped with and N was formed to a thickness of 1.0 μm.

Next, Al and A are deposited on the ZnTe active layer.
At the same time, g was doped to form an n-type ZnMgMgSeTe compound semiconductor layer of 2.0 μm. At this time, high-purity Al metal is used as the n-type dopant source, the doping amount of Al is such that the carrier concentration in the crystal is -10 ¹⁸ cm ^-3 , and the doping amount of Ag is about half the doping amount of Al. And the amount.

Next, Al and A are deposited on the n-type ZnMgSeTe layer so that the carrier concentration is 5 × 10 ¹⁸ cm ^−3.
An n-type ZnTe contact layer was formed to a thickness of 0.05 μm by doping g.

After forming each layer as described above, the layer was taken out from the crystal growth apparatus, and a gold electrode was formed on the ZnTe substrate side, n.
A W (tungsten) electrode was formed on the type ZnTe contact layer side to fabricate a light emitting diode.

When the above light emitting diode was energized and the change in luminescence intensity over time was measured, there was almost no change in luminescence intensity and stable luminescence characteristics were obtained.

For comparison, only N is used as a dopant and Z is used.
A light emitting diode having an nTe buffer layer and an active layer was prepared. When the time-dependent change in the emission intensity of this light-emitting diode was measured under the same conditions as in the above measurement, it was revealed that the emission intensity significantly decreased with time as compared with the light-emitting diode of this embodiment.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments.

In addition to the ZnTe compound semiconductor and ZnMgSeTe compound semiconductor described in the present embodiment, ZnTe
Such as ZnMgTe and ZnM that are lattice-matched to the substrate
gSe, BeMgTe, BeMgSeTe, BeZnM
gTe, CdZnTe, CdSeTe, CdZnSeT
It can also be applied to the case of forming a p-type semiconductor or an n-type semiconductor made of a compound such as e or CdMgSe.

[0040]

According to the present invention, when a ZnTe-based compound semiconductor is crystal-grown, an element occupying the Zn lattice position, and the energy when the Zn lattice position is occupied forms vacancies at the Zn lattice position. Since the first dopant element (Ag, Cu, etc.), which is more stable than the energy of, is doped, a ZnTe-based compound semiconductor single crystal having a high carrier concentration and a low crystal defect density is relatively easily manufactured. It becomes possible to do. And this ZnTe
By using a compound semiconductor single crystal as a substrate,
It is possible to manufacture a highly reliable semiconductor element.

Continued front page    (72) Inventor Kenji Sato             3-17-35, Shinsōnan, Toda City, Saitama Prefecture Stocks             Company Nikko Materials Toda Factory (72) Inventor Satoshi Asahi             3-17-35, Shinsōnan, Toda City, Saitama Prefecture Stocks             Company Nikko Materials Toda Factory F-term (reference) 4G077 AA02 AA03 AB01 BE26 CD01                       DA05 DB08 HA02                 5F041 CA41 CA49 CA55 CA57 CA58

Claims (11)

[Claims] 1. A first dopant, which is an element occupying a Zn lattice position and whose energy when occupying the Zn lattice position is more stable than energy when forming a hole at the Zn lattice position, is doped. A ZnTe-based compound semiconductor single crystal characterized in that. 2. The first dopant is Ag or C.
The ZnTe-based compound semiconductor single crystal according to claim 1, comprising at least one of u. 3. The method according to claim 1, wherein the first dopant is doped with a second dopant composed of an element that occupies a Te lattice position and controls the conductivity type to p-type. 2. A ZnTe-based compound semiconductor single crystal according to item 2. 4. The second dopant is N, P or As.
The ZnTe-based compound semiconductor single crystal according to claim 3, comprising at least one of the above. 5. A p-type carrier concentration of 1 × 10 ¹⁸ cm
^-3 or more and carrier mobility is 40 cm ² / V · s
It is ec or more, The ZnTe type compound semiconductor single crystal of Claim 3 or Claim 4 characterized by the above-mentioned. 6. The p-type ZnTe-based compound semiconductor single crystal according to claim 5, which has a resistance of 0.1 Ω · m or less. 7. The ZnTe according to claim 1 or 2, wherein the first dopant and a third dopant made of an element that controls the conductivity type to n-type are doped. Compound semiconductor single crystal. 8. The third dopant is Al, Ga,
The ZnTe-based compound semiconductor single crystal according to claim 7, containing at least one of In and Cl. 9. The n-type carrier concentration is 1 × 10 ¹⁸ cm 2.
^-3 or more and carrier mobility is 130 cm ² / V ·
9. The ZnTe-based compound semiconductor single crystal according to claim 7, wherein the ZnTe-based compound semiconductor single crystal is not less than sec. 10. The ZnTe compound semiconductor single crystal according to claim 9, having a resistance of 0.05 Ω · m or less. 11. A semiconductor device comprising the ZnTe-based compound semiconductor single crystal according to claim 1 as a base.