JPH0677529A - Light emitting semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a light emitting semiconductor device radiating a light whose wavelength is longer than the natural oscillation wavelenth of semiconductor constituting a light emitting layer. CONSTITUTION:The title device has at least one multilayered structure wherein a semiconductor layer (silicon layer 2) is sandwiched by electrochemically stable material layers (silicon germanium compound layers 3). Fine porous structure 5 is constituted on the section of the semiconductor layer which section is exposed on the section of the multilayered structure. By injecting a carrier in the fine porous structure 5, a light whose wavelength is longer than the natural oscillation wavelength of the semiconductor constituting the porous structure 5 is radiated. On the substrate, at least the one multilayered structure wherein the semiconductor layer (silicon layer 2) is sandwiched by the electrochemically stable material (silicon germanium compound layers 3) is formed and subjected to anodic oxidation, thereby forming the fine porous structure 5 on the section of the semiconductor layer (silicon layer 2).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting semiconductor device, and more particularly to a light emitting semiconductor device having a porous structure in a cross section of a semiconductor layer and emitting green or blue light by injecting carriers into the porous structure. The present invention relates to a device and a manufacturing method thereof.

[0002]

2. Description of the Related Art Since silicon crystals have a forbidden band width of about 1.2 eV and an indirect transition type band structure, it has been considered that they do not emit light in the visible light band. However, first, a sponge-like porous structure is formed on the surface by anodizing a silicon substrate, electrons are confined in this porous structure, and a high quantum energy level due to the quantum size effect is given, Attempts have been made to generate visible light by the transition between these high quantum energy levels (NIKKEI MICRODEVICES 1992).
February issue p. 72-76).

FIGS. 4A and 4B are explanatory views of a conventional light emitting semiconductor device. FIG. 4 (A) schematically shows a cross section after anodizing the silicon substrate, and FIG. 4 (B) shows the relationship between the porosity and the energy gap of the surface of the silicon substrate having a porous structure formed by anodizing. There is. In this figure, 31 is a silicon substrate and 32 is a porous structure.

In this case, the anodization is carried out by using the p-type silicon substrate 31 with a volume ratio of hydrofluoric acid and alcohol having a concentration of 50% of 1 :.
Immersed in 1 of the electrolytic solution, the silicon substrate 31 of the p-type positively, and negatively separately provided electrode, a step of flowing a 5 minute current at a current density of about 10 mA / cm ^2.

By this anodization, a porous structure 3 of 20 to 30 Å is formed on the surface of the silicon substrate 31 to a depth of several μm.
2 is formed, but according to the experiment, as shown in FIG. 4B, the energy gap is 1.3 eV when the porosity is 50%, and the energy gap is 1.4 eV when the porosity is 70%.
1.42eV at 80%, 1.55e at 85%
It was 1.78 eV when V and 90%.

[0006]

According to the prior art,
As described above, the energy gap is increased by increasing the porosity of the porous structure formed by anodization, and the energy gap is 1.78 eV when the porosity is 90%. Then, when a carrier is injected into the porous structure 32, orange light is emitted,
Even if anodization is continued for a longer time, the surface is only roughened, the porosity does not increase, and the energy gap does not increase, so that green or blue light cannot be emitted.

According to the present invention, the effective energy gap is increased by increasing the porosity of the porous structure on the surface of the semiconductor layer, particularly the silicon layer, and the green color having a wavelength shorter than the intrinsic emission wavelength of the semiconductor layer, for example, silicon. It is an object of the present invention to provide a light emitting semiconductor device that emits blue or blue light.

[0008]

A light emitting semiconductor device according to the present invention has at least one laminated structure in which a semiconductor layer is sandwiched between electrochemically stable material layers, and is exposed in a cross section of the laminated structure. By adopting a structure having a fine porous structure in the cross section of the semiconductor layer and injecting carriers into this porous structure, light having a wavelength shorter than the natural oscillation wavelength of the semiconductor constituting this porous structure is emitted. I did it.

In this case, the semiconductor layer may be made of silicon so as to emit green or blue light.

Further, in the method for manufacturing a light emitting semiconductor device according to the present invention, a step of forming at least one laminated structure in which a semiconductor layer is sandwiched between electrochemically stable material layers on a substrate, and the laminated structure. A step of forming a fine porous structure on the cross section of the semiconductor layer exposed on the cross section of the laminated structure by anodization was adopted.

In this case, the semiconductor layer may be made of silicon, and the electrochemically stable material layer may be made of a silicon germanium compound so that green or blue light is emitted.

[0012]

According to the present invention, when at least one pair of laminated structures in which a semiconductor layer such as silicon is sandwiched by electrochemically stable material layers such as silicon germanium compound is formed and the cross section of the laminated structure is anodized, A sponge-like porous structure finer than 20 to 30 Å is likely to occur in the cross section of the semiconductor layer such as silicon exposed in this cross section, the quantum size effect efficiently occurs, and the effective energy gap can be increased. Light having a shorter wavelength can be emitted as compared with the case where a conventional semiconductor surface is anodized to form a sponge.

The cause of the formation of the extremely fine porous structure in the cross section of the semiconductor layer has not yet been clarified, but the semiconductor layer made of silicon or the like is made of an electrochemically stable material such as a silicon germanium compound. When a layered structure sandwiched by layers is formed and its cross section is anodized, the semiconductor layers that make up this layered structure are already as thin as a sponge-like porous structure, so anodization forms a large surface. It is speculated that a sponge-like porous structure is formed, which leaves a semiconductor filament that is thinner and has a sufficient length as compared with the related art.

[0014]

EXAMPLES Examples of the present invention will be described below. (First Embodiment) FIGS. 1A to 1D are explanatory views of a manufacturing process of a light emitting semiconductor device according to a first embodiment of the present invention. In this figure, 1 is a silicon substrate, 2 is a silicon layer, 3 is a silicon germanium compound layer, 4 is an opening, 5 is a porous structure, and 6 is an electrode.

A method of manufacturing the light emitting semiconductor device according to the first embodiment of the present invention will be described with reference to the manufacturing process explanatory diagram.

First step (see FIG. 1 (A)) A silicon substrate 1 having a thickness of 20 is formed by MOVPE.
~ 30Å silicon (Si) layer 2 and thickness 20 ~ 30Å
The silicon germanium compound (SiGe) layers 3 are alternately grown epitaxially to a thickness of several μm. The MOVPE method can be replaced with another growth method such as MOCVD method and MBE method.

Second step (see FIG. 1B) In this laminated structure, an opening 4 having a diameter of several μm reaching the surface of the silicon substrate 1 is formed by a photolithography technique.

Third step (see FIG. 1C) The laminated structure formed in the second step is immersed in an electrolytic solution having a concentration of hydrofluoric acid and alcohol of 50% and a volume ratio of 1: 1.
Make this laminated structure positive and make the separately provided electrode negative,
Anodization is performed by passing a current having a current density of about 10 mA / cm ² for 5 minutes. As a result, the cross section of the silicon layer 2 exposed on the side wall of the opening 4 has a width of 20 to 3 in the lateral direction of the silicon layer 2.
A porous structure 5 finer than 0 Å and having a wide energy gap is formed, and a silicon germanium compound (Si
The Ge) layer 3 remains unanodized.

Fourth Step (see FIG. 1D) An electrode 6 made of gold or the like is formed on the silicon layer 2 which is the uppermost layer of the laminated structure. When a voltage is applied between the silicon substrate 1 and the electrode 6 to inject carriers, electrons and holes are recombined through the wide energy gap of the fine porous structure 5 to emit green or blue light. To do. If this electrode is made of ITO, the light emitted from the fine porous structure 5 can be emitted to the outside through the ITO electrode.

In this description, in the first step, the thickness of the silicon germanium compound (SiGe) layer 3 is set to 20 to 30 Å, which is about the same as that of the silicon layer, but this thickness is not so important and contributes to light emission. It is desirable to make the silicon layer as thin as possible in order to increase the density of the silicon layer.

Further, in this description, the opening 4 having a diameter of several μm was formed in the second step, but instead of this, the width of several μm.
Alternatively, a structure may be adopted in which the groove is formed to divide the laminated structure into two in a plane. In this case, one electrode is formed on each of the uppermost silicon layers on both sides of the groove, and a current can be passed between them.

In this embodiment, the silicon germanium compound layer is used as the electrochemically stable material layer because the lattice constant of silicon and germanium is 4%.
This is because the approximations are made only by varying the degree, and it is easy to grow by stacking single crystal layers with good crystallinity.

Further, in this embodiment, the silicon layer is used as the light emitting layer having the porous structure, but the same effect is obtained even when other semiconductor layers are used according to the principle described above. However, when the compound semiconductor layer is used, it is difficult to form a fine porous structure with the composition of the compound semiconductor by anodization.

(Second Embodiment) FIG. 2 is a structural explanatory view of a light emitting semiconductor device according to a second embodiment of the present invention. In this figure, 11 is a silicon substrate, 12, 14, 16, 17, 1
9, 21, 22, 24, 26 are silicon germanium compound layers, 13, 15, 18, 20, 23, 25 are silicon layers, 27 _B , 27 _G , 27 _R are openings, 28 _B , 2
8 _G and 28 _R are porous structures, and 29 _B , 29 _G and 29 _R are electrodes.

The structure of the second embodiment of the present invention will be described in conjunction with the description of the method for manufacturing the light emitting semiconductor device.

First Step A silicon germanium compound layer 12, a silicon layer 13, a silicon germanium compound layer 14, a silicon layer 15, and a silicon layer each having a large thickness (about 60 Å to 100 Å) on the silicon substrate 11 by MOCVD. The germanium compound layer 16 is sequentially grown.

Second Step This silicon germanium compound layer 12 and silicon layer 1
3, silicon germanium compound layer 14, silicon layer 1
5. The opening 27 _R is formed in the laminated body including the silicon germanium compound layer 16 by the photolithography technique.

Third Step This silicon germanium compound layer 12 and silicon layer 1
3, silicon germanium compound layer 14, silicon layer 1
5. The laminated body composed of the silicon germanium compound layer 16 was immersed in an electrolyte solution having a volume ratio of hydrofluoric acid and alcohol of 1: 1 at a concentration of 50%, and the laminated body was made positive and negatively applied to a separately provided electrode at 10 mA / a silicon layer 13 exposed on the side wall of the opening 27 _R by anodizing by applying a current of about cm ² .
A fine porous structure 28 _R is formed on the cross section of 15.

Fourth Step: After the resist is embedded in the opening 27 _R , the thickness of each layer is slightly thin (about 30Å to 40Å), the silicon germanium compound layer 17, the silicon layer 18, the silicon germanium compound layer 19 and the silicon are formed. A layer 20 and a silicon germanium compound layer 21 are grown. At this time, a single crystal layer grows on the silicon germanium compound layer 16, but a polycrystalline layer grows on the resist embedded in the opening 27 _R.

Fifth Step This silicon germanium compound layer 17 and silicon layer 1
8, silicon germanium compound layer 19, silicon layer 2
0, an opening 27 _G is formed in the laminated body including the silicon germanium compound layer 21 by a photolithography technique.

Sixth step By the same step as the third step, the side wall of the opening 27 _G of the laminated body composed of the silicon germanium compound layer 17, the silicon layer 18, the silicon germanium compound layer 19, the silicon layer 20, and the silicon germanium compound layer 21. A fine porous structure 28 _G is formed on the cross section of the silicon layers 18 and 20 exposed at the bottom.

Seventh step: After the resist is buried in the opening 27 _G , the thickness of each layer is thinner (about 10Å to 20Å) on the entire surface, the silicon germanium compound layer 22, the silicon layer 23, the silicon germanium compound layer 24, and the silicon. A layer 25 and a silicon germanium compound layer 26 are grown. At this time, a single crystal layer grows on the silicon germanium compound layer 21, but on the polycrystalline layer grown on the resist embedded in the opening 27 _R and on the resist embedded in the opening 27 _G. A polycrystalline layer grows.

Eighth Process This silicon germanium compound layer 22, silicon layer 2
3, silicon germanium compound layer 24, silicon layer 2
5. The opening 27 _B is formed in the laminated body including the silicon germanium compound layer 26 by the photolithography technique.

Ninth step By the same step as the third step, the side wall of the opening 27 _B of the laminated body including the silicon germanium compound layer 22, the silicon layer 23, the silicon germanium compound layer 24, the silicon layer 25, and the silicon germanium compound layer 26. A fine porous structure 28 _B is formed on the cross section of the silicon layers 23 and 25 exposed at the bottom.

[0035] After embedding the resist to the tenth step opening 27 _B, the entire surface by depositing gold, patterned electrodes 29 _B, and form a 29 _G, 29 _R. After that, the polycrystalline layer grown on the openings 27 _R , 27 _G is removed by etching to remove the openings 27 _R , 27 _G ,
The resist in 27 _B is removed.

In this embodiment, the silicon layer 13,
The thickness of 15 is made thick (about 60Å to 100Å), and the thickness of the silicon layers 18 and 20 is made thinner (30Å to 40).
About Å), since the thickness of the silicon layer 23, 25 and thinner than that (about 10A～20A), the same degree of anodization, the porous structure 28 in the opening 27 _R
And _R, and the porous structure 28 _G during opening 27 _G, the opening 27 _B
Comparing the inner porous structures 28 _B , these porous structures become higher in porosity and finer in this order, and as a result,
Their energy gaps increase in this order.

Therefore, by adjusting the thickness of each semiconductor layer and the time of anodization, the porous structure 28 _R ,
The energy gaps of the porous structure 28 _G and the porous structure 28 _B can be designed to have values corresponding to red, green and blue wavelengths. And the electrodes 29 _B , 29 _G , and 29 _R
By selectively passing a current between the silicon substrate 11 and the silicon substrate 11 to inject carriers, red, green and blue lights can be emitted.

FIG. 3 is a wavelength characteristic diagram of the light emitting semiconductor device of the second embodiment of the present invention. This figure shows that in the light emitting semiconductor device according to the second embodiment of the present invention, the energy gap is changed to red () by changing the degree of miniaturization of the porous structure 28 _R , the porous structure 28 _G and the porous structure 28 _B. a),
It shows that the values can be designed to correspond to the wavelengths of green (b) and blue (c).

As described above, the two-dimensional color display device can be constructed by combining the red, green and blue lights into one pixel.

In the above embodiments, the thickness of each semiconductor layer was designed so as to have an energy gap corresponding to the wavelengths of red, green and blue light. The energy gaps corresponding to the wavelengths of red, green, and blue light are designed by changing the degree of miniaturization of the porous structures 28 _R , 28 _G , and 28 _B by making them the same and adjusting the anodization time. You can also do it.

[0041]

As described above, according to the present invention,
The emission wavelength (color) can be adjusted by forming a semiconductor having a large energy gap such as silicon in a layered form and performing anodization on this semiconductor layer, which is a comparatively easy process. As well as
It can be used as a light source for an optoelectronic IC (OEIC), and a two-dimensional color display device can be formed by combining light sources having different emission wavelengths (colors) into pixels.

[Brief description of drawings]

1A to 1D are explanatory views of a manufacturing process of a light emitting semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a structural explanatory view of a light emitting semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a wavelength characteristic diagram of a light emitting semiconductor device according to a second embodiment of the present invention.

4A and 4B are explanatory views of a conventional light emitting semiconductor device.

[Explanation of symbols]

1 Silicon Substrate 2 Silicon Layer 3 Silicon Germanium Compound Layer 4 Opening 5 Porous Structure 6 Electrode 11 Silicon Substrate 12, 14, 16, 17, 19, 21, 21, 22, 24, 2
6 Silicon Germanium Compound Layer 13, 15, 18, 20, 23, 25 Silicon Layer 27 _B , 27 _G , 27 _R Opening 28 _B , 28 _G , 28 _R Porous Structure 29 _B , 29 _G , 29 _R Electrode

Claims (4)

[Claims] 1. A semiconductor device having at least one laminated structure in which a semiconductor layer is sandwiched between electrochemically stable material layers, and a fine porous structure is formed in a cross section of the semiconductor layer exposed in the cross section of the laminated structure. A light emitting semiconductor device, characterized in that by injecting a carrier into the fine porous structure, light having a wavelength shorter than an intrinsic emission wavelength of a semiconductor forming the porous structure is emitted. 2. The light emitting semiconductor device according to claim 1, wherein the semiconductor layer is made of silicon and emits green or blue light. 3. A step of forming at least one laminated structure in which a semiconductor layer is sandwiched between electrochemically stable material layers on a substrate, and an anodization of the laminated structure exposes a cross section of the laminated structure. A method of manufacturing a light emitting semiconductor device, comprising the step of forming a fine porous structure in a cross section of a semiconductor layer. 4. The light emitting semiconductor device according to claim 3, wherein the semiconductor layer is made of silicon, and the electrochemically stable material layer is made of a silicon germanium compound, and emits green or blue light. Manufacturing method.