JPH0677527A - Si light emitting element and its manufacture - Google Patents

Abstract

PURPOSE:To realize a new Si light emitting element capable of electric light emission wherein fragility is reinforced, by constituting a quantum wire type porous Si layer, a conductive polymer layer forming a PN junction with the porous Si layer, and electrodes corresponding with them. CONSTITUTION:On the single surface of an insulative substrate 5, an ITO film or a thin gold film as an electrode 3 for an Si layer is formed, a B-doped P-type poly Si layer 6 is deposited on the film and dipped in hydrofluoric acid, and anodic oxidation is performed, thereby forming a quantum-sized porous Si layer 1 in the surface layer region of the poly Si layer 6. On the layer 1, a conductive polymer layer 2 having N-type conductivity is deposited, thereon an ITO film as an electrode 4 for a polymer layer is formed by sputtering, an etching mask 7 is formed, the ITO is sputtered and etched, and the conductive polymer layer 2 is subjected to ashing. Hence the ITO being the electrode 3 for the Si layer is exposed, ohmic contacts 8, 8' of metal are formed for the electrodes 3, 4, and an Si light emitting element can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly to a hetero diode type Si light emitting device capable of emitting light.

In recent years, attempts have been made to obtain visible light emission by reducing the size of Si to generate a quantum effect.

[0003]

2. Description of the Related Art Si has an indirect transition type bandgap corresponding to near-infrared light, and it has been conventionally thought that it would be difficult to emit light, and its application to a light emitting element has been abandoned. But,
Also in Si, it was found that the band structure changes when the size is miniaturized to the extent that the quantum effect is exhibited (tens to hundreds of liters).

The band structure becomes a pseudo direct transition type,
Subband of the band gap energy with the formation effectively increases ^{ΔEg = h 2 {(1 /} 4m * e d 2) + (1 / 4m * h d 2)} ( here, h is Planck's constant, d is the quantum size diameter ) Can be seen.

If the light emission of Si is achieved by electrical means,
Optoelectronic integrated circuits and displays using Si substrates can be realized. Porous Si containing quantum-size thin wires can be formed relatively easily over a large area in the process of anodizing Si in a hydrofluoric acid aqueous solution. Therefore, application to low-cost display devices is expected.

[0006]

Although the quantum wire-like porous Si has a possibility of emitting light, its specific constitution as an electroluminescent device has not been known yet. Also, the quantum wire-shaped Si region is fragile. Porous Si is an assembly in which bent columnar Si having a diameter of several tens of liters is spatially separated from each other. Therefore, the mechanical strength is extremely weak.

An object of the present invention is to electrically porous Si,
That is, it is an object of the present invention to provide a novel Si light emitting device capable of emitting light from a Si quantum wire bundle and reinforcing its fragility, and a method for manufacturing the same.

[0008]

The Si light emitting device of the present invention has a quantum wire-like porous Si layer having p-type conductivity and an n-type conductivity, and forms a pn junction with the porous Si layer. A conductive polymer layer and the porous Si layer,
An electrode for each of the conductive polymer layers.

The conductive polymer is a polypyrrole derivative,
It is preferably formed of a polyacetylene derivative or a polyaniline derivative. The conductive polymer layer is preferably laminated on the porous Si layer by an electrochemical film forming method or a vapor film forming method.

[0010]

When the p-type porous Si layer and the n-type conductive polymer layer are joined and a bias voltage is applied in the forward direction or the reverse direction through the respective electrodes, electrons are injected into the porous Si layer and recombination light emission occurs. The emission wavelength depends on the quantum wire diameter.

The conductive polymer layer bonded to the porous Si layer also serves to reinforce the fragile quantum wire bundle. Hereinafter, the present invention will be described in more detail based on examples.

[0012]

EXAMPLE FIG. 1 is a sectional view showing a main part of a manufacturing process of a Si light emitting device according to an example. As shown in FIG. 1A, an ITO film or an extremely thin gold film is formed as a Si layer electrode 3 on one surface of an insulating substrate 5 made of transparent quartz. On top of this, a B-doped p-type poly-Si layer 6 is deposited.

For example, a silane gas diluted with hydrogen is used as a Si source, and diborane is used as a p-type dopant, and a p-type poly-Si layer having a thickness of several thousand Å to several μm and a carrier concentration of 7 × 10 ¹⁷ cm ^-3 is formed by plasma CVD. To film.

Next, as shown in FIG. 2A, the poly-Si layer 6 is dipped in an aqueous solution of hydrofluoric acid (HF 10 to 48% by weight), connected to the anode of the DC bias power source E _B , and opposed to each other. The immersed reference electrode such as platinum is connected to the cathode of the DC bias power source E _B.

Direct current is applied at a current density of 10 to 70 mA / cm ² and anodic oxidation is performed to form a porous Si region 1 from the surface of the poly Si layer 6. The porosity of poly-Si is
Once the surface starts to be perforated, the electric field concentrates on the bent surface, so that anodic oxidation preferentially proceeds in the depth direction. With the passage of time, the hole diameter does not expand so much, but deep holes are drilled.

The presence of holes is necessary for the anodizing reaction. Compared to the bottom of the hole, the side wall surface of the hole is flat, so the electric field is weak,
Since the depletion layer spreads on the surface, the supply of holes is small. Holes have a small radius of curvature and are preferentially generated at the bottom of the hole where the electric field is concentrated. Therefore, anodic oxidation preferentially proceeds in the depth direction. The oxide film is immediately dissolved in the hydrofluoric acid solution.

However, perforations do not always proceed vertically from the surface due to the generation of voids and the like due to etching. Rather, as shown in the enlarged view of FIG. 2B, it becomes deeper while bending.

Therefore, the perforation diameter is determined not only by the etching time but also by the HF aqueous solution concentration and temperature. When the perforation rate exceeds 50%, holes 11 are formed as shown in the figure.
The Si quantum wires 10 separated by are formed. S
The i quantum wire diameter can be 40 to 50 Å.

In this way, the quantum-sized porous Si layer 1 is formed in the surface layer region of the poly-Si layer 6 dipped in the HF aqueous solution.
Is formed. Instead of the p-type poly layer 6, an acceptor-doped p-type amorphous Si layer may be used. In the present specification, unless otherwise specified, "poly S
“I” includes “amorphous Si”.

As shown in FIG. 1B, a conductive polymer layer 2 having n-type conductivity is deposited on the porous Si layer 1. For example, polyvinyl alcohol (PVA) and iron trichloride (FeCl ₃ ) are dissolved in water or ethyl alcohol, and this is applied to the surface of the Si layer by spin coating, dried and heat-treated to polymerize. Where F
eCl ₃ is a polymerization oxidizer (promoter).

Next, when the polyvinyl alcohol film was cooled to -15 ° C. and exposed to pyrrole and water vapor, a polypyrrole derivative film (polypyrrole-polyvinyl alcohol composite film) was obtained.
Is obtained. By such a vapor deposition method, the conductive polymer layer 2 having n-type conductivity is formed.

The conductive polymer layer 2 may be formed by a method other than the vapor deposition method. For example, PVA, pyrrole, FeCl
Polymerization method in which the mixture of ₃ is dissolved in water or ethyl alcohol, coated, dried, and heat-treated to form a polypyrrole-polyvinyl alcohol composite film, or the polySi layer is directly immersed in a mixed solution of PVA, pyrrole, and FeCl _3. It is possible to use an electrochemical film forming method or the like in which the film is deposited while being polymerized by an electric field.

For details of these conductive polymer layer forming methods, see, for example, the following paper (T. Ojio and
S. Miyata, Polymer Journal, 18 , 95 (1986), YEWhang,
JHHan, T. Motobe, T. Watanabe and S. Miyata, Synth
etic Metals, 45 , 151 (1991), JHHan, T.Motobe, YE
Whang and S. Miyata, Synthetic Metals, 45 , 261 (199
1)).

As shown in FIG. 1C, an ITO film is sputter-deposited as an electrode 4 for the polymer layer on the n-type conductive polymer layer 2. A photoresist film is applied on the polymer layer electrode 4, exposed and developed to form a photoresist etching mask 7.

As shown in FIG. 1D, using this mask 7, ITO, which is the polymer layer electrode 4, is first sputter-etched, and then the conductive polymer layer 2 is ashed in oxygen plasma.

Further, the poly-Si layer 6 is etched in a chlorine or hydrofluoric acid gas plasma. The ITO that is the Si layer electrode 3 is exposed in the etched region.
After that, the etching mask is removed.

After that, ohmic contacts 8 and 8'of a metal such as Al are made to the electrodes 3 and 4 made of ITO.
Is formed, the Si light emitting element is completed. The conductive polymer layer 2 is bonded to at least the top of the Si quantum wire,
Reinforce the mechanical strength of the brittle porous Si layer 1. In particular, in the case of the electric field polymerization film formation method, the conductive polymer layer 2 can be said to be more preferable because it penetrates into the upper portion of the pores 11 by the electric field.

The above manufacturing process is easy to increase the area. For example, an XY matrix type display can be created. FIG. 3 shows a display device in which a large number of Si light emitting devices Zij are separated from each other on a transparent insulating substrate and arranged in a matrix. FIG. 3A is a plan view and FIG. 3B is an enlarged perspective view of a pixel portion.

A stripe-shaped Si layer electrode (lower transparent electrode) Yj is formed on the substrate 20 in the Y direction, and p is formed thereon.
A light emitting device Zij composed of a type porous Si layer and an n-type conductive polymer layer is formed, and a conductive polymer layer electrode (upper metal electrode) Xij is formed thereon. It will be apparent to those skilled in the art that the planarization treatment may be performed before forming the upper metal electrode.

Since the radiated light from the Si light emitting element is emitted from the lower transparent substrate side, the striped electrode Yj must be transparent, but Xi may be a metal (opaque). External quantum efficiency can also be increased by using a high-reflectance metal. Of the matrix of light emitting elements, only Zij to which the signal voltage is applied emits light. A switching transistor or the like may be further coupled to each light emitting element.

These Si light emitting elements have a forward voltage of 5
20V for reverse voltage under bias condition of V or more
It emits light under a bias condition of a certain degree. The emission intensity depends on the applied voltage (and therefore the flowing current), but the emission wavelength is S
i depends on the quantum wire diameter. The smaller the diameter, the shorter the wavelength of light emitted.

Instead of the backside light emitting type, it is also possible to use a surface light emitting type. In this case, the upper electrode is a transparent electrode. In addition, a Si single crystal substrate is used instead of the insulating substrate, and p-type S
The i layer can also be a single crystal.

As the conductive polymer, other polypyrrole derivatives other than those in the above examples may be used, or a polyaniline dielectric or a polyacetylene dielectric may be used. However, the polyaniline type and the polyacetylene type lack durability in an oxygen atmosphere.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various changes, improvements, combinations and the like can be made.

[0035]

As described above with reference to the embodiments, according to the present invention, quantum wire-like porous Si can be relatively easily formed.
It is possible to provide a Si light-emitting element whose fragility is reinforced by using.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of a manufacturing process of an Si light emitting device according to an example.

FIG. 2 is a cross-sectional view showing a method for forming a porous Si layer and a schematic configuration of a porous region.

FIG. 3 is a plan view and a schematic perspective view showing an XY matrix type display device.

[Explanation of symbols]

 1 Porous Si Layer 2 Conductive Polymer Layer 3 Electrode for Si Layer 4 Electrode for Polymer Layer 5 Insulator Substrate 6 Poly Si Layer 7 Etching Mask 8, 8 ′ Ohmic Contact 10 Si Quantum Wire 11 Void 20 Substrate Zij Si Light-Emitting Element

Claims (6)

[Claims] 1. A quantum wire-like porous Si layer (1) having p-type conductivity, a conductive polymer layer (2) having n-type conductivity and forming a pn junction with the porous Si layer, A Si light emitting device having electrodes (3) and (4) for the porous Si layer (1) and the conductive polymer layer (2), respectively. 2. The Si light emitting device according to claim 1, wherein the conductive polymer (2) is a polypyrrole derivative, a polyacetylene derivative or a polyaniline derivative. 3. One of the electrodes (3) is an insulating substrate (5).
The Si light emission according to claim 1 or 2, wherein the porous Si layer (1) is formed on the surface of a p-type poly-Si layer (6) formed on one of the electrodes (3). element. 4. The Si light-emitting device according to claim 3, wherein the insulator substrate (5) and one of the electrodes (3) are transparent to radiated light from the Si light-emitting device. 5. A quantum wire-shaped porous S on a p-type Si layer.
Si light emission including a step of forming an i region (1) and a step of stacking an n-type conductive polymer layer (2) on the porous Si region (1) by an electrochemical film forming method or a vapor film forming method. Device manufacturing method. 6. The p-type Si layer is a poly-Si layer (6), and the step of forming the porous Si region (1) communicates with the surface layer of the poly-Si layer by anodic oxidation in an aqueous solution of hydrofluoric acid. The method for manufacturing a Si light emitting device according to claim 5, further comprising the step of forming a quantum wire-shaped Si region by forming a hole.