JP3228481B2 - Light emitting thin film fabrication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a light emitting thin film, and more particularly to a method for producing a light emitting thin film for emitting light of silicon, germanium, or a mixed crystal thereof as a non-light emitting substance.

[0002]

2. Description of the Related Art Conventionally, silicon (hereinafter referred to as Si), germanium (hereinafter referred to as Ge), and a mixed crystal thereof (hereinafter referred to as SiGe mixed crystal).
Has an indirect transition-type energy band structure, and therefore differs from a substance having a direct transition-type energy band structure, such as a group III-V compound semiconductor, in that the transition between bands due to excited electrons is No luminescence due to recombination could be observed. However, in recent years, photoluminescence generated from a microcrystalline phase has been observed. This report can be found, for example, in LT Canham, Appl.Phys. Lett. 57, 1046 (199
0), S. Furukawa, Phys. Rev. B 38, 5726 (1988), H. Takag
i, Appl. Phys. Lett. 56, 2379 (1990). Regarding Ge, photoluminescence is observed from the surface of modified Ge produced by a plasma etching method using CF ₄ / O ₂ . Si or G mentioned above
It is considered that the light emitting action such as e occurs due to the quantum size effect of the microcrystal. That is, when the size of a substance becomes a so-called ultrafine particle, the energy levels of the bands become discrete, and as a result, light is emitted upon recombination.

[0003]

The luminous bodies described in the above-mentioned documents produce ultrafine particles by the respective production methods. Conventional methods for producing ultrafine particles use an electrochemical method, a pure chemical method, or a plasma etching method to produce ultrafine particles. Each of the manufacturing methods disclosed in each document is a method of forming a desired shape by shaving a raw material. The conventional manufacturing method is
There is no particular problem in terms of its quantification and reproducibility. An object of the present invention is to provide a thin film having a microcrystalline structure manufactured by a method completely different from a conventional microcrystal manufacturing method, and to be able to manufacture the microcrystal with good control, and to continuously control the size and morphology of the microcrystal. An object of the present invention is to provide a method for producing a light emitting thin film that can be changed and can control the width of the emission wavelength with a high degree of freedom.

[0004]

According to the present invention, there is provided a method for producing a light emitting thin film, wherein the (111) plane of an oxide made of an alkaline earth metal such as magnesium oxide (MgO) is immersed in hot phosphoric acid.
Many triangular pyramids formed by (100) plane
Forming a (111) plane having a projection, and having a projection
Silicon and germanium on the (111) plane
Of any of the mixed crystal systems of
The tip portion of the deposited layer formed by deposition is used as a light emitting portion . In the above method for forming a light emitting thin film, preferably, the deposited layer has a thickness of 100 Å or more and 1 μm or less.

[0005]

In the present invention, the following processing is performed as a basic premise for forming the (111) plane of magnesium oxide (MgO). First, MgO (1
11) In order to form a plane, the [111] direction is determined by X-ray diffraction in MgO, which is a face-centered cubic crystal, and cut by a diamond cutter in a direction perpendicular to this direction. next,
In order to remove cutting marks on the fine powder of alumina, the cut (111) plane is polished until it becomes a mirror surface. Thereafter, the substrate is immersed in hot phosphoric acid at about 70 ° C. for 15 minutes to form a (111) plane to be a light emitting thin film substrate.
The (100) plane perpendicular to the [111] azimuth axis of MgO prepared as described above is a plane in which a large number of triangular pyramids formed from three (100) planes are present regularly. The height of the triangular pyramid is several microns. Any of Si, Ge, and SiGe mixed crystal system is deposited on the (111) plane of the MgO thus manufactured by using a chemical vapor deposition method or a physical vapor deposition method, thereby forming a deposited layer. This deposited layer forms a large number of triangular pyramid projections on its surface corresponding to the shape of the many (111) triangular pyramids.
The pointed shape of the projection makes it possible to cause a light emission phenomenon based on the quantum size effect of the microcrystal.
A layer deposited on the chemically treated (111) plane
When the film thickness exceeds 100 angstroms, photoluminescence is observed. However, above 1 micron, the intensity of photoluminescence decreases.
This is because the pointed shape of the pyramid on the surface of the deposited layer is broken and the quantum size effect of the microcrystal is weakened because the thickness of the deposited layer is increased.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an MgO substrate.
A (111) plane is formed on the upper surface of the substrate 1 in the drawing.
The method of forming the (111) plane is as described in the section of the operation. The (111) direction is found, cut perpendicular to the [111] direction, and by performing the above-described required processing, the (111) direction is obtained. ) Surface 1a can be formed. On the (111) plane, the innumerable triangular pyramid-shaped projections 3 are formed. Reference numeral 3a indicates a (100) plane on which the triangular pyramidal projection 3 is formed. Next, as shown in FIG. 2, a deposition layer 2 is formed on the (111) plane. The material of the deposition layer 2 is any of Si, Ge, and a mixed crystal of SiGe. Any technique can be used for forming the deposition layer 2. When deposition starts on the (111) plane of the substrate, the deposition layer 2 is deposited according to the shape of the (111) plane. Therefore, the shape of the surface of the deposition layer 2 also follows the shape of the (111) plane, and a large number of protrusions having a triangular pyramid shape are formed. This sedimentary layer 2
The thickness of the deposited layer 2 is 1
When the thickness is more than 00 Å, a quantum size effect of microcrystals occurs at the pointed portion. Thus, when excitation light is applied, light is generated from the tips of a number of protrusions on the surface of the deposition layer 2. The thickness of the deposition layer 2
When appropriately adjusted within a predetermined range, it is possible to control the shape of the tip of the projection on the surface of the deposition layer, whereby it is possible to arbitrarily adjust the wavelength of emitted light, etc., and to have extremely excellent controllability. Can make light. When the deposition on the surface of the substrate 1 is further continued, the thickness of the deposition layer 2 increases, and as shown in FIG. 3, the pyramid shape of the protrusion formed on the surface of the deposition layer is broken. Therefore, when the thickness of the deposited layer 2 exceeds 1 μm, the quantum size effect of the microcrystal is reduced, the light emission phenomenon is weakened, and it becomes difficult to obtain light of a desired light intensity. In the above embodiment, MgO was described as the material of the substrate 1. However, any material can be used as long as it is an oxide made of an alkaline earth metal.

[0007]

As is clear from the above description, according to the present invention, the present invention has a myriad of regular projections in a method different from the conventional method, and the tip of each projection has a quantum size effect of the microcrystal. A light emitting thin film exhibiting the above characteristics can be produced. Further, according to this method for producing a light emitting thin film, it is easy to adjust the thickness and the like of the thin film, so that there is an effect that the light emitting conditions can be easily controlled.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an MgO substrate having a (111) plane.

FIG. 2 is a longitudinal sectional view of a light emitting thin film in a state where a deposition layer is formed on a (111) plane.

FIG. 3 is a longitudinal sectional view of a light emitting thin film in a state where a deposited layer is too thick.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 1a ... (111) surface 2 ... Deposited layer 3 ... Protrusion

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Claims (2)

(57) [Claims] 1. An oxide (1) of an alkaline earth metal oxide
11) By soaking the surface in hot phosphoric acid, the (100) surface
(111) having a large number of triangular pyramid projections formed of
Forming a surface, said has a projection (111) surface of silicon, germanium, the deposition layer or the deposited layer was formed, was formed by depositing on the protrusion of these mixed crystals From the point of the
A method for producing a light emitting thin film, wherein the light emitting portion is used. 2. The method according to claim 1, wherein the deposited layer has a thickness of 100 Å or more and 1 μm or less.