JPS62126642A - Amorphous compound semiconductor - Google Patents

Abstract

PURPOSE:To improve thermal stability of III-V and II-VI compound semiconductors, which have, e.g., an amorphous phase with low thermal stability, by constituting an amorphous compound semiconductor with a composition in a miscibility gap appearing in a mixed crystal of two kinds of compounds or in the vicinity of said gap. CONSTITUTION:An amorphous compound semiconductor ZnSxO1-x becomes an amorphous state depending on a composition (x). The amorphous material ZnSxO1-x is hard to crystallize in heat treatment. As embodiments of mixed crystals other than ZnSxO1-x, e.g., GaAsxSb1-x and InPxSb1-x can be considered as III-V compound semiconductors. A distance between bondings of GaAs and GaSb is as large as 7.5%. In this mixed crystal, a miscibility gap is present in the composition in the vicinity of the intermediate part, i.e., in the vicinity of x=0.5. The difference in distance between the bondings of InP and InSb is also as large as 9.9%. The miscibility gas is present in the composition close to InP.

Description

[Detailed description of the invention] The present invention relates to amorphous compound semiconductors.

[Conventional technology]

Amorphous semiconductors, including so-called amorphous silicon, have many advantages such as a wide selection of substrates, excellent economic efficiency, and the ability to continuously change the composition to selectively develop desired properties. In recent years, it has been applied to, for example, solar cells, thin film transistors, photoreceptors, etc., and has attracted attention.

On the other hand, in the field of crystals, III-V group, I
BACKGROUND ART Compound semiconductors such as I-VI group semiconductors are being researched and put into practical use as materials for light emitting devices because of their large band gaps. Compound semiconductors such as Group IIIiV and Group II-VI have strong ionic bonding properties and are difficult to become amorphous, and even if they become amorphous, they have low structural stability and tend to crystallize easily, so they are not suitable as amorphous semiconductors. Applications are still at the basic research stage.

Specifically, for example, III-V group amorphous GaAs is 28
0°C, II-VI group amorphous ZnSe is 180°C, 0.
It has been reported that amorphous Z n Te crystallizes at 100° C. for 2 to 3 hours.

As described above, in order to apply a compound semiconductor as an amorphous structure, the low structural stability against heat and the like has been a major technical issue that hinders its practical application.

[Purpose and outline of the invention]

An object of the present invention is to solve the conventional problems and provide a novel amorphous compound semiconductor with high structural stability against heat and the like.

The above-mentioned problems are achieved by the amorphous compound semiconductor of the present invention, which is characterized in that it has a composition in or near the cap that appears in a mixed crystal of two or more types of compounds.

[Detailed description and examples of the invention]

To explain the configuration of the present invention in more detail, for example, A.
Two types of compound semiconductors AQ and AR are assumed, each having Q, A, and R as constituent atoms.

Now, when forming a solid solution AQ R with these two types of compound semiconductors, if the difference between the bond distance between the atoms of the compound semiconductor 1-x AQ and the bond distance of AR is large to some extent, the mixed crystal AQ, which is the crystal phase, The composition range in which R is not formed, the so-called i-x impossibility gap (formerly 5cibility gap)
Gap (also called solubility gap) exists.

The miscibility gap is a composition range in which two types of compounds (for example, compound semiconductors) that constitute a crystal phase cannot be dissolved as a single crystal phase, that is, a mixed crystal. [For example, it is explained in detail in Nishinaga Yo, Kazumasa Hiramatsu; "Miscibility of compound semiconductor mixed crystals J, Applied Physics 50.1065 (1981)." By using a known amorphous semiconductor manufacturing method such as plasma chemical vapor deposition, sputtering, or ion blating, the substrate is cooled to prevent precipitation of the crystalline phase and forcibly separate the two. A compound semiconductor is dissolved in a solid solution to form an amorphous solid solution.In a solid solution in which a miscibility gap exists in a mixed crystal, the network is disordered due to the large bond distance difference between the two types of compound semiconductors. Figure 1 shows the case where one S atom enters the ZnO network to replace an O atom in the case of ZnSO, a II-Vl group compound semiconductor, as a solid solution. This is a two-dimensional exaggerated depiction of the network disturbance that occurs in Zn.
-5 bond distance is 2.33A, Zn-0 bond distance is 1
．． 98A, disturbances as depicted in Figure 1 are expected. When more 0 atoms are substituted for S atoms, this disorder spreads throughout the network, and the solid solution ZnS 2 O becomes amorphous. This disorder of 1-x is due to an internal factor, the difference in bond distance between Zn-3 and Zn-0, so unless the positional relationship of the atoms is changed by heat treatment etc., in other words, it will be close to the melting point. The disorder in this network cannot be lost unless it is heated to a certain level. That is, the thermal stability of the structure of the amorphous compound semiconductor constructed in this manner is dramatically improved.

The composition range in which the thermal stability of this amorphous phase is dramatically improved is the composition within or near the miscibility gap where mixed crystals cannot be formed.

Thus, according to the present invention, for example, two types of compounds AQ,
By configuring an amorphous compound semiconductor with a composition within or near the miscibility gap appearing in the AR mixed crystal, for example, I.
The thermal stability of II-V and II-VI compound semiconductors can be improved.

Next, as a specific example of the present invention, an amorphous compound semiconductor ZnSO will be described.

It is difficult to form an amorphous phase in both the 1-x 11-Vl group compound semiconductors ZnS and ZnO, and there has been no report on the formation of an amorphous phase. Furthermore, even if an amorphous phase is formed, it is considered to have a very unstable structure against heat and is likely to crystallize. On the other hand, ZnS Oi-x constructed according to the present invention becomes amorphous depending on the composition X, and amorphous ZnS
O does not crystallize even after heat treatment x 1 −
x Kui. Figure 2 shows ZnS powder as the target and Ar-0
2 is an example of an X-ray diffraction image when a ZnSO film is deposited on a water-cooled glass substrate by the reactive high-frequency sputtering method in a mixed gas atmosphere. CuKα rays are used for the irradiation X-rays. This ZnS
In the O film, a diffraction peak due to the ZnS crystal plane appears only at 2e=29° in the X>0.5(7) l−x composition range. FIG. 2 is a plot of the composition dependence of the diffraction intensity appearing at 20-29°. Second
As shown in the figure, the diffraction peak decreases as X becomes smaller, and when X≦0.5, no diffraction peak appears at all. Furthermore, although we have not investigated films with a composition of x<0.3, at least in the composition range of 0.3≦X≦0.5, no crystal diffraction peaks other than 2θ=29° appear, indicating that the film is amorphous. I understand something. Figure 3 shows amorphous ZnS with x=0°3 fabricated using this reactive high-frequency sputtering method.
This is a comparison of X-ray diffraction images before and after the heat treatment when the O film was heat treated at x l-x (10 Torr) in vacuum for 400'0.1 hour. The wide diffraction around 2θ-25° seen in the two diffraction images is due to the glass substrate. In FIG. 3, no crystal diffraction peak is observed even after heat treatment, indicating that no crystallization occurred.

Figure 4 shows amorphous ZnS with x=0.3 and 0.52.
The optical absorption spectrum of the O film is x l -x. Figure 5 shows the photoluminescence spectrum at room temperature when the 365 nm emission line of an ultra-high pressure mercury lamp is used as the excitation light. As shown in Figs. 4 and 5, the band gap energy of the amorphous ZnSO film can be changed from 3.4 eV to 3.2 eV by changing 1-x from 0.3 to 0.52. To,
It is also seen that the peak wavelength of photoluminescence changes from 650 nm to 700 nm. That is, by continuously changing X, it is possible to continuously control the band gap energy and the emission peak wavelength.

As described above, it is difficult for ZnS and ZnO to form an amorphous phase due to their strong ionic bonding properties, and there have been no reports of a combination of these to create an amorphous phase. In contrast, according to the present invention, it is possible to construct an amorphous semiconductor having a highly thermally stable structure from II-VI group compound semiconductors ZnS and ZnO. In addition, the amorphous compound semiconductor ZnSO can be made into a pan by changing X.
1-x decap energy and emission peak wavelength can be controlled, and the band gap energy is 3.2 to 3.
．． Since it has a large value of 4 eV, it can be applied to amorphous light emitting materials in the visible range, transparent conductive films, etc.

In this way, the present invention utilizes the miscibility gap that appears in the mixed crystal of two types of compound semiconductors with different bond distances between adjacent atoms to improve the thermal stability of the amorphous structure against heat treatment. Groups III-V and II
- Not only binary compound semiconductors such as Group VI compound semiconductors, but also ternary compound semiconductors, such as l-111-V
An amorphous compound semiconductor can also be constituted by a mixed crystal containing a compound semiconductor that is considered to have a high degree of ionicity in bonds such as group I2 and is difficult to become amorphous.

Examples x l for mixed crystals other than ZnS O
-x, for example, as a III-V compound semiconductor, G
xi-xxl-x such as aAs Sb and InP Sb can be considered. The bond distance between GaAs and GaSb is 7
．． The composition is as large as 5%, and the composition of the mixed crystal is near the middle, that is,
A Mitsubishiity-φ cap exists near x=0.5. Also, the bond distance difference between InP and InSb is 9.9%.
A robustness cap exists in a composition that is thick and closer to InP.

As an example of a II-VI group compound semiconductor, for example, Zn5eOxi-x"ZnTeO, which has not been reported to form a mixed crystal, may be considered.ZnS e l-
The bond distance difference between x and ZnO is 21%, and the difference between ZnTe and Zn
The bond distance difference with O is as large as 28%, and both Zn5e O and ZnTe O
The entire composition range of l-x corresponds to the miscibility gap.

〔Effect of the invention〕

As explained below, according to the present invention, III-
By configuring an amorphous material from group V and group II-VI compound semiconductors, etc. with a composition within or near the miscibility gap, it is possible to make it difficult to crystallize even by heat treatment. III-V, which can improve the thermal stability of the structure and is sufficiently durable for practical use.
A group or II-VI amorphous compound semiconductor can be constituted. Furthermore, by changing the composition within the composition range that can form a stable amorphous phase, it becomes possible to continuously control the band gap energy and the emission peak wavelength when applied to light emitting materials. When applied to a device, it becomes possible to freely select the necessary characteristics.

[Brief explanation of drawings]

FIG. 1 shows Z, which is an example of the amorphous compound semiconductor of the present invention.
x l − to explain the structure of nS O
x is a schematic diagram. FIG. 2 shows Z, which is an example of the amorphous compound semiconductor of the present invention.
This is an X-ray diffraction diagram of nS 2 O. x 1 - x The horizontal axis is the X value, and the vertical axis is the diffraction intensity corrected for the difference in film thickness. Figure 3 shows 0.3 before and after heat treatment of ZnSO.
0.7 is an X-ray diffraction pattern in which as dep is before heat treatment, and 400°C l hr (vacuum) is an X-ray diffraction pattern after heat treatment at 400°C in vacuum for 1 hour. Figure 4 shows ZnSO films with compositions X of 1-x 0.3 and 0.52 (7) amorphous ZnSOx.
FIG. 3 is a curve diagram showing the optical absorption characteristics of the l-x film at room temperature. The horizontal axis is photon energy (eV), and the vertical axis is αhυ (α:
Absorption coefficient (hr: photon energy) is shown. Figure 5 shows amorphous ZnS with X of 0.3 and 0.52.
It is a curve diagram showing the photoluminescence spectrum of an O film at room temperature when the x l -x 365 nm emission line of an ultra-high pressure mercury lamp is used as excitation light. The lower side of the horizontal axis is photon energy (eV), and the upper side is wavelength (nm).
), and the vertical axis indicates the relative value of photoluminescence intensity. Agent Patent Attorney Minoru Yamashita To Hirabacho IV Reprinted Animal Figure 3 20 30 40 50 60 7
0 8r times re-extraction 2θ (agricultural)

Claims (1)

[Claims] An amorphous compound semiconductor characterized by having a composition within or near a miscibility gap appearing in a mixed crystal of two or more types of compounds.