KR950006965B1 - Forming method of zn3p2 epitaxial thin film - Google Patents

Abstract

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Description

A method of forming a Zn3P2 (zinc phosphorus compound) epitaxial thin film in an InP (indium phosphorus) semiconductor crystal

1 to 6 are cross-sectional views showing the manufacturing process of the present invention.

* Explanation of symbols for main parts of the drawings

1: InP semiconductor substrate

2: In _x Ga _1-x As _y P _1-y (1> x≥0.53, 0 <y≤1) semiconductor epitaxy layer

_{3: In x Ga 1-x} As y P a In _x In _1-y layer is mixed in the _{'Ga 1-x'} As _y P _1-y area

4: In _{x ''} Ga _{1-x ''} P region where Ga is mixed on the InP substrate

5: Zn ₃ P ₂ precipitation layer

The present invention relates to a method for forming an epitaxial layer of a Zn ₃ P ₂ semiconductor in an InP-based semiconductor material, wherein In _x Ga _x ^-1 As _y P _1-y /InP(1>x≥0.53, 0 <y≤ 1) When zinc (Zn) is diffused into the heterojunction structure, the heterojunction structure is formed by mixing In and Ga near the interface thereof, and In _{x '} Ga _1-x' As _y P _1-y / In _{x ''} Ga _{1- The present} invention relates to a method of effectively growing a Zn ₃ P ₂ epitaxial layer in an In _{x ''} Ga _{1-x ''} P region while alloying with _{x ''} P.

Zn ₃ P ₂ crystal is a direct transition semiconductor material with a bandgap of 1.5 eV and is known as the most ideal material for detecting solar chips in the air atmosphere (AM1).

Due to these characteristics, Zn ₃ P ₂ is very likely to be used in solar cells, photodiodes, and photonic integrated devices.

Until now, Zn ₃ P ₂ thin films have been grown by vapor transporation, hot-wall deposition, photo CVD, and the like. Si substrates and Mg substrates are mainly used for growing thin films.

The Zn ₃ P ₂ thin films produced by the above method are mostly polycrystalline thin films. The main reason for using a polycrystalline Zn ₃ P ₂ thin film is that the production method is easier and cheaper than a single crystal thin film, which is advantageous for practical use as a solar cell.

An additional reason is that there is no suitable semiconductor substrate capable of epitaxially growing single crystal thin films, and technically epitaxial growth is very difficult.

In spite of these technical problems, the material properties of the monocrystalline thin film are superior to the polycrystalline thin film. Therefore, if the single crystal thin film can be grown, it may be used for special applications requiring high performance solar cells.

In particular, when single crystals are grown on InP-based substrates that are widely used as photoelectric materials, Zn ₃ P ₂ / InP epitaxial structures may be useful as materials for fabricating photoelectric integrated devices.

In the present invention, a method of forming a Zn ₃ P ₂ thin film by diffusing Zn in a Ga _In AsP / InP heterostructure, in a similar manner, is performed on In _0.53 Ga _0.47 As / InP superlattice or Ga _In AsP / InP superlattice. Zn was diffused to form a Zn ₃ P ₂ / Zn ₃ As ₂ superlattice epitaxial layer.

However, when the Ga _In AsP / InP (or Ga _In AsP / InP) superlattice is used, a very thin Zn ₃ P ₂ / Zn ₃ As ₂ multilayer structure having a thickness of several to tens of nm (10 ^-9 m) is obtained. In this structure, Zn ₃ P ₂ and other Zn ₃ As ₂ thin film layers coexist, which is less useful as a solar cell, and the thickness of these thin films is too thin compared to an appropriate thickness that can be manufactured with a general solar cell. There is this.

Accordingly, an object of the present invention is to provide a method for growing a Zn ₃ P ₂ single crystal thin film having excellent properties on an InP substrate for melting into an optoelectronic material.

In order to achieve the above object, the present invention provides a method for growing an epitaxial layer on a semiconductor crystal, in which In _x Ga _1-x As _y P _1-y (1> _x ≧ 0.53, 0 <y <) on an InP substrate. 1) growing a single crystal thin film, and heat treating the Zn diffusion source at a temperature of 450 ° C. to 700 ° C. for 1 hour to 20 hours to form a heterogeneous layer of the InP substrate and the In _x Ga _1-x As _y P _1-y single crystal thin film layer. Zn diffuses in the junction structure, and the heterojunction structure of the InP substrate and the In _x Ga _1-x As _y P _1-y single crystal thin film layer is In _{x '} Ga _1-x' As _y P _1-y single crystal thin film layer and In _x. as the mixing _{'' Ga 1-x ''} P structure of the single-crystal thin film layer includes a step in which the precipitation of Zn ₃ P ₂ layer in the in _{x '' Ga 1-x ''} P single crystal thin film layer.

The detailed process of the present invention will be described below with reference to the accompanying drawings.

1 shows an InP semiconductor substrate 1.

[Step 1]

As shown in FIG. 2, the single crystal thin film 2 of In _x Ga _1-x As _y P _1-y (1> x≥0.53, 0 <y≤1) lattice matched on the InP substrate 1 is epitaxially formed. It is a step of growing into a structure.

The composition of In _x Ga _1-x As _y P _1-y lattice matched to the InP substrate 1 is given by the relationship of x = (1-0.4836y) / (1-0.31y), The allowable range for x is ± 0.02y.

In the In _x Ga _1-x As _y P _1-y layer 2 composition, when y = 1, it corresponds to a ternary alloy of In _x Ga _1-x As.

The epitaxial growth method is a crystal growth method of a semiconductor thin film which is generally used, that is, liquid phase epitaxy, vapor phase epitaxy, metalorganic chemical vapor deposition, and epitaxy before compound injection. (Chemical beam epitaxy) method or the like can be used.

[Step 2]

In FIG. 3, Zn is diffused into the substrate 2 and the layer 2 forming the In _x Ga _1-x As _y P _1-y / InP heterojunction structure. In this process, Zn ₃ P ₂ powder, ZnP ₂ powder or a mixed powder thereof may be used as the diffusion source of Zn.

In addition, in order to protect the surface of the InGaAsP layer 2, a mixed powder of Zn ₃ P ₂ + InP + GaAs can be used.

Heat treatment for diffusion is heat-treated for 1 hour, 20 hours at a temperature of 450 ℃ to 700 ℃.

The process of forming the Zn ₃ P ₂ layer 5 by the Zn diffusion process is as follows.

First, Zn diffusion promotes mutual mixing of In elements and Ga elements at the interface of the heterojunction structure of In _x Ga _1-x As _y P _1-y / InP (layer 2 and substrate 1).

In this case, the intermixing between the As element and the P element is not promoted by Zn diffusion.

By the In-Ga intermixing, In _{x '} Ga _1-x' As _y P _1-y region (3) in which In is mixed at the top of the interface and In _{x ''} Ga _1-x in which Ga is mixed at the bottom of the interface _'' P region 4 is shown in FIG. 4.

If the next Zn diffusion is sufficiently maintained, Zn ₃ P ₂ crystals 5 are deposited into the epitaxial layer in the In _{x ''} Ga _{1-x ''} P region 4.

The principle that the Zn ₃ P ₂ epitaxial layer 5 is formed is that as the Ga is mixed with the InP crystal having a zincblende lattice structure, the lattice constant gradually decreases, thereby In _{x ''} Ga _1- having a specific x '' composition. _{An x ''} P alloy can be lattice matched to a Zn ₃ P ₂ crystal with tetragonal lattice structure in an array of 2 x 2 x 2 in the a, b, and c axial directions, thus providing a specific In _{x ''} Ga Zn ₃ P ₂ crystals preferentially precipitate in the _{1-x ''} P region.

Here, Zn diffusion and the mixing of In and Ga proceed uniformly in the direction parallel to the interface between InGaAsP / InP (layer 2 and substrate 1), so that a specific x can form a lattice match with Zn ₃ P _2. The specific region of <sub>``</sub> In <sub>x ''</sub> Ga <sub>1-x ''</sub> P having the `` composition _'' is unfolded in a direction parallel to the interface to form a layered Zn ₃ P ₂ precipitate 5 as shown in FIG.

[Step 3]

Zn ₃ P _2, layer 5 is shown as InGaASP layer (2), (3) and _{In x '' Ga 1-x} '' P step of etching the layer (4) above in Figure 6.

The Zn ₃ P ₂ epitaxial layer 5 formed in the In _{x ``} Ga _{1-x ''} P layer 4 may be used as it is in FIG. 5, or may be In _x Ga as in FIG. 6a. _{A structure in which the 1-x} As _y P _1-y layer (2) and the In _{x '} Ga _1-x' As _y P _1-y layer (3) were removed, or the Zn ₃ P ₂ layer (5) as shown in FIG. In _{x ''} Ga _{1-x ''} P (4) can be used to remove the structure.

As shown in FIG. 6A, the removal of the InGaAsP layers 2 and 3 on the In _{x ``} Ga _{1-x ''} P layer 4 is performed at room temperature by H ₃ PO ₄ : H ₂ O ₂ : H ₂ O (= 1: 1: 5 ~ 1: 1: 25) using a solution can be achieved by wet etching (wet etching).

As described above, according to the present invention, a Zn ₃ P ₂ layer can be formed in an InP-based semiconductor to obtain a photovoltaic material having excellent properties as well as to grow a thick Zn ₃ P ₂ single crystal, thereby making it possible to manufacture a highly efficient solar cell. Do.

Claims (4)

In the method of growing an epitaxial layer on a semiconductor crystal, In _x Ga _1-x As _y P _1-y lattice matched on an InP substrate 1 (1> x ≧ 0.53, 0 <y ≦ 1; x = (1-0.4836y) / (1-0.31y) ± 0.02y) growing the single crystal thin film 2 and heat-treating for about 1 to 20 hours at a temperature of 450 ° C. to 700 ° C. using a Zn diffusion source. Zn is diffused into the heterojunction structure of the InP substrate 1 and the In _x Ga _1-x As _y P _1-y single crystal thin film layer 2 so that the InP substrate 1 and the In _x Ga _1-x As _y The heterojunction structure of the P _1-y single crystal thin film layer (2) is In _{x '} Ga _1-x' As _y P _1-y single crystal thin film layer (3) and In _{x ''} Ga _{1-x ''} P single crystal thin film layer (4) Zn ₃ P ₂ epi in the InP-based semiconductor, comprising the step of depositing Zn ₃ P ₂ (5) in the In _{x ''} Ga _{1-x ''} P single crystal thin film layer 4 while being mixed in the structure of Method of Forming a Tactical Layer. The In _x Ga _1-x As _y P _1-y layer (2) and the In _x Ga _1-x As _y P _1-y layer (3) on the Zn ₃ P ₂ layer (5). And selectively etching the In _{x ''} Ga _{1-x ''} P layer (4). 12. A method of forming a Zn ₃ P ₂ epitaxial layer in an InP-based semiconductor. 3. The In _x Ga _1-x As _y P _1-y layer (2) and the In _{x '} Ga _1-x' As _y P _1-y layer (3) and the In _{x ''} Ga Wet etching using a solution of H ₃ PO ₄ : H ₂ O ₂ : H ₂ O (1: 1: 5 to l: 1: 25) to selectively etch the _{1-x ''} P layer 4 A method of forming a Zn ₃ P ₂ epitaxial layer in an InP-based semiconductor. The InP-based semiconductor according to claim 1, wherein the Zn diffusion source is Zn ₃ P ₂ , ZnP ₂ , Zn ₃ P ₂ + ZnP ₂ , Zn ₃ P ₂ + InP, Zn ₃ P ₂ + InP + GaAs. A method of forming a Zn ₃ P ₂ epitaxial layer within.