JPS5944791B2 - semiconductor element - Google Patents

Description

[Detailed description of the invention] The present invention relates to amorphous silicon carbide (hereinafter referred to as a- It is called Sil-xCx.

The present invention relates to a semiconductor device having a different junction, that is, a heterojunction, with a composition x where 0<X<1. Conventionally, Be, CdS, and the like have been known as substances that have high optical conductivity and high dark resistance, have long-term charge retention ability, and can further apply a high electric field.

However, these substances are toxic and belong to polluting substances, and there is a strong desire for semiconductor elements using non-polluting materials to replace them. In recent years, amorphous silicon (a-Si
) is attracting attention as having strong photoconductivity, but the room temperature dark specific resistance of this material is at most about 10"3 Ωcm, and the breakdown electric field of current/voltage characteristics is low, making it difficult to apply high voltages and high electric fields. However, it has the drawbacks of large dark current and poor long-term charge retention ability.

In recent years, the manufacturing method and existence of a-Si7-xCx have been revealed by phil.

Mag, pl, Vol. 35, (1978), etc., discloses that if the carbon concentration x is increased, the energy gap (Eg) increases up to a certain concentration, and at the same time, the room temperature resistivity also increases. However, no reports have been found that examine the photoconductivity of this material. As a result of a detailed study of the characteristics of this a-Sil-xCx, the present invention found that this carbon-containing material has a high room temperature resistivity, excellent photoconductivity, and that the charge injected into this material is This is based on the discovery that it has the ability to be transported.

Furthermore, by forming a heterojunction of a relatively small first layer with a relatively large composition x and a relatively large second layer, the first layer has a wide photosensitive wavelength range and the second layer has a high withstand voltage. A photoconductive semiconductor element with good properties and properties was obtained.
The object of the present invention is to have high photoconductivity for light in the visible range,
An object of the present invention is to provide a semiconductor element using a material that has high voltage resistance, low dark current, and is non-polluting.

Another object of the present invention is to provide a semiconductor device having excellent photoconductive and photovoltaic functions.

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``A further object of the present invention is to provide a semiconductor element that has high mechanical strength and is suitable for application to, for example, a photosensitive layer for electrophotography.A further object of the present invention is to provide a semiconductor element that has high mechanical strength and is suitable for application to, for example, a photosensitive layer for electrophotography. The object of the present invention is to provide a semiconductor device that can be manufactured easily.

The above-mentioned object of the present invention is achieved by providing a semiconductor device having a heterojunction of amorphous silicon carbide having different compositions.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an example of the basic configuration of a semiconductor device based on the present invention.

1 is a conductive substrate, 2 and 3 are a-Sll-XcC layers, both have different compositions x, and have a heterojunction at the interface between the two.

4 is a transparent conductive film which may be made of Pt, Au, In2O, snO2, etc.

5 and 6 are electrodes for connecting the element to an external electric circuit.

7 is a power source, 8 is a load resistor, and when using the photoconductive element, a switch 9 is connected to the power source 7 side in the figure.

When utilizing the photovoltaic energy of the element, the switch 9 is connected to the load resistor 10 side. 11 is incident light.

The a-Sil-XcX layers 2 and 3 are selected to have a relatively small composition of x, and include a first layer 2 that is sensitive to irradiation light in the visible range and easily generates photoexcited charge carriers, and a phase. The first layer 2 is selected to have a composition with a relatively large value of x, and has a relatively large energy gap (Eg) for injecting the generated charge carriers and transporting them. and a second layer 3 of color. The first is the photosensitive function for a wide visible wavelength range.
By forming a heterojunction with a second layer 2VC and a second layer 3VC having high electric field and high voltage resistance and injection charge transport functions, photoconductivity and photovoltaic power with high sensitivity and high voltage resistance are achieved. The device is configured to constitute a magnetic semiconductor element. Note that either layer 2 or 3 in FIG. 1 may be the first layer or the second layer. FIG. 2 shows another basic configuration example of a semiconductor element having a photoconductive function according to the present invention.

In FIG. 2, the same reference numbers as in FIG. 1 indicate similar elements.

The difference from FIG. 1 is that a transparent conductive film 13 is provided on a transparent substrate 12, and elements are formed on this. With this configuration, it is possible to manufacture a semiconductor element that is also sensitive to the light 14 incident from the substrate 12 side. As described above, the semiconductor device of the present invention has the following characteristics: (1) When designed as a photoconductive device that has high voltage resistance against externally applied voltage and high photosensitivity,
The composition of the second layer may be greatly changed from that of the first layer, and the second layer may be designed to have a high resistance. When designing a device, the second layer is doped with impurities to make it low in resistance, reduce absorption of externally incident light, and facilitate transport of charge carriers photoexcited in the first layer. Therefore, the thickness of the second layer may be made smaller than that of the first layer.

The semiconductor element of the present invention can be manufactured, for example, as follows.

The substrate may be one that has a smooth surface and can withstand the temperature at which the photoconductor layer is deposited, for example from 150 to 400°C.
It doesn't matter whether it is crystalline or amorphous. For example, semiconductors such as Si single crystals, metals such as stainless steel and aluminum: quartz glass, ceramics, or insulators such as plastic films that can withstand the above temperatures, with conductive coatings such as metals or metal oxides on the surface are used. It can be done. After cleaning the surfaces of these boards, place them in a glow discharge device.
The substrate temperature is increased appropriately. A mixed gas having a first composition ratio in which a silicon compound exhibiting a gaseous state with a stable structure at room temperature, such as SiH4, and a carbon compound exhibiting a gaseous state having a stable structure at room temperature, such as C2H4, at a desired concentration ratio; Each of the mixed gases having a composition ratio of 2 is diluted with an inert gas such as argon, and these diluted mixed gases are sequentially introduced into the glow discharge device and heated to 10-2 to 101T0r.
By sequentially decomposing the films for a desired time using glow discharge under a pressure of about R, each film has a desired composition and film thickness on the substrate. A heterojunction consisting of a layer of a-Sil-XcX is formed. Furthermore, when forming the second layer after the first layer, or forming each layer by the reverse process, by gradually changing the concentration ratio of silicon compounds and carbon compounds in the raw material gas, inclined heterogeneous bonding can be achieved. Of course, it can be formed.

In particular, when it is necessary to deposit an a-Sil-XcX layer to which impurities have been added, an appropriate gaseous compound of group or V group elements, such as B2H6 or PH3, may be added to the diluted mixed gas.

a-Sil-XcX with heterojunction then deposited
A layer of a transparent conductive material is appropriately formed on the film using a conventional technique to form a semiconductor element of the present invention.

When manufacturing the element of the present invention, the manufacturing method is not limited to the above-mentioned manufacturing method. The present invention will be explained in more detail below based on Examples.

[Element manufacturing example]

The substrate used was Si single crystal (p-type 10 Ω·Cm), stainless steel, or quartz glass with an In2O3:SnO2 (TO) transparent conductive film formed thereon.

In a 13.5MH2 high frequency glow discharge device, the substrate temperature was
The temperature was maintained at 50°C, and the temperature was 20v01. Introducing Ar gas containing 0% SiH4,
．． Glow discharge decomposition was performed at a pressure of 1T0rr.

Next, Ar was mixed with C2H4 and SiH4 at a concentration of 18v010%. A gas was introduced and glow discharge decomposition was performed at the same 0.1 T0rr to deposit a second layer with a thickness of about 1 μm.

After that, Si single crystal, a-S deposited on stainless steel substrate
Approximately 150% of ITO was deposited on the film with ll-XcX heterojunction.
0X. A transparent electrode was formed by depositing an AuSb alloy of approximately 1000 A on each film having a heterojunction on a quartz glass substrate with a S1 single crystal, stainless steel/ITO coating, and a semiconductor element having photoconductive and photovoltaic functions was formed. .
As a result of measurement using the X-ray microanalysis method, the composition X of the second layer was approximately 35%. The photoelectric characteristics of these devices were measured using a tungsten lamp with an A light source at an illuminance of 230L.
I went with x.

[Example 1] Figure 3 shows a-Sil-
The characteristics of an element having a heterojunction of XcX and an ITO transparent conductive film are shown.

In the figure, a curve 15 shows the dark current when the Si substrate is negatively biased, and a curve 16 shows the photocurrent. Curve 17 shows the dark current when the substrate is positively biased, and curve 18,
19 indicates photocurrent. Here, the direction of the photocurrent shown by curve 19 flows in the direction of the applied voltage, but the photocurrent shown by curve 18 is opposite to the direction of the applied voltage, and from this it is clear that a photovoltaic force appears. .

The photovoltaic force of this device is approximately 350 mV at an open circuit voltage and approximately 7 x 10-0 A/Cn at an illuminance of 230 Lx.
i was obtained. On the other hand, as for the characteristics of the photoconductive element, at the above illuminance, a photocurrent/dark current ratio of about 1 x 103 times is obtained, and furthermore, the dark current density is 1 x 10-10 A/Cr! The applied voltage exceeding i is about 10, and the average electric field at this time is about 3×
Obtain 104V/Cm. For comparison, it is currently impossible to obtain a dark current density of 1.times.10.sup.10 A/Cd or less using a layer made only of a-Si. [Example 2] A device on a stainless steel substrate with a TO surface electrode also had almost the same characteristics as shown in Fig. 3, both in terms of dark current/photocurrent characteristics and photovoltaic force characteristics when the TO surface electrode was negatively biased. Indicated.

[Example 3] Figure 4 shows the characteristics of a device on a Si substrate having an approximately 1000 Af) Au-Sb alloy film as a surface electrode.

Curves 20 and 21 show the dark current photocurrent when the substrate is negatively biased, respectively. Further, curves 22 and 23 show dark current and photocurrent when the substrate is positively biased. The photocurrent density is lower than in FIG. 3, but this is due to the use of a relatively thick semi-transparent conductive film. However, the dark current did not change particularly. Furthermore, since the Au-Sb electrode was used, no photovoltaic force was generated and very similar characteristics were exhibited in both the positive and negative bias directions, probably because the barrier at the interface between the electrode and a-Sil-XcX was reduced. Therefore, it can be concluded that a good dissimilar bonding surface is formed.

[Example 4] An element on a stainless steel substrate having an AuSb alloy film of about 1000 A0 as a surface electrode as in Example 3 also exhibits almost the same characteristics as in FIG. 4.

[Example 5] The a-Si, -XCx and conventional elements used in the fabrication of the elements of the previous examples, whose photoconductive films are Se, CdS, etc., were scratched with the tip of stainless steel tweezers, and then mechanically removed. The strength was compared.

Jumei's elements using Se and CdS were easily damaged, but
Although the element according to the present invention was pressed with considerable force, no mechanical damage was observed.

FIG. 5 shows the spectral sensitivity distribution of the photoconductive characteristics of the device of the example described above. Curves 24 and 25 each use Au as the surface electrode.
●Characteristics of elements containing Sb and ITO. curve 26
shows the spectral sensitivity distribution of an a-Si single layer film (approximately 0.7 μm) as a relative value. Curves 24 and 25 have the highest sensitivity at about 490 nm, and on the longer wavelength side, the sensitivity decreases, showing a tendency almost similar to curve 26. As mentioned above, the composition of the second layer of the device of this example is x=0.35, and since this composition has an energy gap of about 2.3 and V, the second layer alone cannot achieve this effect. There is no sensitivity on the long wavelength side. Since the overall sensitivity on the long wavelength side shows a similar tendency to the sensitivity distribution of a-Si, this element
It is clear that charge carriers photoexcited in the i-layer are injected and transported into the second layer. On the other hand, the reason why the sensitivity of the element decreases at wavelengths shorter than 490 nm is thought to be because there is a second layer with a composition x = 0.35 on the light incident side, and this layer absorbs the incident light. . This decrease in sensitivity at short wavelengths can be avoided by increasing the composition x of the second layer and increasing the energy gap. On the other hand, if the configuration is such that light is incident from the direction of the first layer, it becomes possible to guide the incident light to the first layer without being attenuated by the second layer. When the device of the present invention is used as a photovoltaic device, high electric field resistance is not required, so it is sufficient to use a light-transmitting second layer that is thinner than the first layer and doped with low resistance.

By doing so, it is possible to solve the drawback of light absorption in the p-type layer, which is a drawback of the current a-Si p-11n homojunction photovoltaic element. Furthermore, the device of the present invention can be applied to the field of electrophotography technology, where a high-voltage surface charge is applied and the surface charge is selectively discharged by utilizing photoconductivity by selective irradiation with light for use in printing, etc. For example, the surface electrode 4 may be removed from the structure shown in FIGS. 1 and 2, and the design may be designed to increase the voltage resistance of the element.

As described above in detail, in the present invention, the composition x
The present invention provides a semiconductor device using a heterojunction of a-Si and xCx that can continuously control the relative composition x.
By assigning the photoexcited carrier generation function to the first layer with a relatively large composition x and the functions of light transmittance and electric field resistance as well as the transport function of the photoexcited carriers to the second layer with a relatively large composition x, each layer can be This allows us to make full use of its unique features.

Therefore, the device of the present invention can provide a photoconductive device (1) that has high sensitivity to light in the visible light range, is resistant to high electric fields and high voltages, and has a small dark current.

(2) A photoconductive element with high mechanical strength can be provided, and is extremely useful especially for applications in the field of electrophotography where wear resistance is required.

(3) It is possible to avoid attenuation of incident light in the p layer, which was a drawback of p-1-n homojunction a-Si photovoltaic elements.

(4) The temperature for forming dissimilar junctions is low, no heat treatment is required after formation, and since it is amorphous, there is a wide selection range of substrate materials and substrate shapes, and manufacturing is easy and flexible depending on the purpose of use. It is possible to provide an element having the shape of .

(5) The basic constituent materials are non-toxic and non-polluting.

It has the following effects and has extremely great industrial value.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing the basic configuration of the semiconductor device of the present invention, and FIGS. 3 and 4 show the relationship between applied voltage and dark current/photocurrent in an embodiment of the semiconductor device of the present invention. diagram showing,
FIG. 5 is a diagram showing the relationship between photocurrent and incident light wavelength in one embodiment of the semiconductor device of the present invention. 1... Conductive substrate, 2, 3... a-S
i, -XCx layer, 4...transparent conductive film, 5,6...
...Electrode, 7...Power supply, 8...
Load resistance, 9... switch.

Claims (1)

[Claims] 1 A conductive substrate and a first conductive substrate formed on this substrate.
an amorphous silicon carbide layer formed on the first layer and a second layer formed on the first layer.
an amorphous silicon carbide layer, the first and second amorphous silicon carbide are Si_1_−_xC_x (0<x<1
), the two layers have different X values, and at least one of the amorphous silicon carbide layers contains a p-type or n-type impurity.