JPS6050973A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device in which irregular lattice is alleviated to activate the features of a hetero junction by interposing a semiconductor layer which has the intermediate of chemical compositions of both semiconductor layers of different band gaps therebetween when forming the hetero junction by the two semiconductor layers. CONSTITUTION:An N type layer 2 made of hydrogenated amorphous Si, an I type layer 3 and a P type window layer 4 for forming hetero junction are laminated on a conductive substrate 1 as a hetero junction semiconductor device made of layers having different band gaps. In this construction, an intermediate layer 5 is interposed additionally between the layers 3 and 4, thereby alleviating the irregular lattice to the layers 3, 4. The layer 5 employs SiH4 of raw material gas used for the layer 3 and gas produced by introducing hydrocarbon gas into the derivative gas in a short time, and formed by glow discharge decomposition. The thickness of the layer 5 at this time is approx. 5-150Angstrom , and the thickness except this reduces the effect instead, and is not accordingly accepted. Thereafter, a transparent conductive film 6 having current collecting electrodes 7 is attached on the layer 4 as normally.

Description

Detailed Description of the Invention When forming a photovoltaic device mainly made of amorphous silicon (hereinafter abbreviated as a-8i), monoplan and silane derivatives are used as silicon sources on a substrate, and acceptor or donor The raw material residue mixed with added impurities that acts as
Methods for forming the i-layer and manufacturing photovoltaic devices are known in the art.

On the other hand, in 1978, Pankov of CA
carbon-doped amorphous silicon (hereinafter referred to as a-8iC) by et al.
a-8iC:H) was applied to the photovoltaic element, and a-8iC:H
A patent (US Pat. No. 4,109,271) has been published in which a photovoltaic device is constructed by forming an /a-8iH heterojunction.

When manufacturing a device by configuring the a-8i n-type layer, i-layer, and p-type layer on the substrate as the first layer, second layer, and third layer, or vice versa, even if doped with impurities, However, the lattice of the doped layer #1 is equivalent to the lattice of a-8i to which no impurity is added. However, →te n / I, p
/l, n/p lattice 11 at each junction interface
The problem of deterioration of bonding properties due to blade alignment occurs';i
There was very little sex. However, the covalent bond radius at the interface between the first and second layers or between the third and third layers is only about 70% of that of silicon.

Table 1 Therefore, the lattice of the a S r C: H layer is a-8i:
Gai a-8iC: H/a- which is very different from the layer lattice of H
It is considered that lattice mismatch occurs at the 84=H interface.

Table #2 Table 2 shows a comparison of the characteristics of homojunction and heterojunction photovoltaic elements. A-8iC generated by glow discharge decomposition of a mixed gas of equal or greater amount of silane and carbonized wood serving as a carbon source in the layer on the incident side of the rim of the heterojunction element.
:H is used, and the amount of carbon in the film is 5 to 20%.

The a-=S+C:H film has a light transmittance of a-si:)l
Intrinsic a-8, which is the photocurrent generation region because it is higher than '<'
Since the amount of light reaching the i:H layer increases, the short-circuit photocurrent (J sc ) is increased compared to the heterojunction element. However, the open circuit voltage (Voc), form factor (FF), and photoelectric conversion efficiency (η) are reduced by 7 to 15 inches. This is considered to be because the aforementioned lattice mismatch occurs at the a-8iC:H/a-8i:H heterojunction interface, causing strain. When strain due to lattice mismatch exists at the junction interface, the localized level density near the interface increases, and the leakage current and series resistance component of the photovoltaic element increase.
It lowers oc and FF. In order to effectively improve the photoelectric conversion efficiency of the photovoltaic device by positioning the a-8iC:H layer with excellent light transparency on the incident light side of the photovoltaic device, it is necessary to There is a need to alleviate inconsistencies.

[Purpose of the invention]

The present invention eliminates the above-mentioned drawbacks and eliminates the heterojunction surface #! Af
The purpose of this invention is to provide a semiconductor device that takes advantage of the characteristics of a heterojunction by alleviating the lattice mismatch that occurs.

[Key points of the invention]

The present invention alleviates lattice mismatch by interposing a layer of semiconductor whose chemical composition is intermediate between the chemical compositions of the semiconductors of both layers between two layers of two types of semiconductors forming a heterojunction. It is something to do.

[Embodiments of the invention]

1 and 4 show the structure of a photovoltaic device according to an embodiment of the present invention. In FIG. 1, an a-si
:) (0 layer 2, a-8i:H 1 layer 3 is laminated, and before laminating the p-type a-8iC:H window layer 4 that forms a heterojunction on top of that, the i-layer Ja-8'iC:H and a-8i:H are produced by introducing a hydrocarbon gas, which serves as a carbon source for a-8iC:H, into the raw material gas monosilane and its derivative gas for a short time and decomposing it by glow discharge. An intermediate layer 5 is formed. Furthermore, a transparent conductive film 6 and a metal current collecting electrode 7 are provided on the window layer 4. This photovoltaic element includes the following:
Depending on the introduction time and amount of hydrocarbon gas added during the formation of the intermediate layer 5, if the hydrocarbon gas is introduced for a period of time such that the film thickness of the intermediate layer 5 is 5 to 150A, the intermediate layer 5 is Compared to the element with the jmijk structure shown in FIG. 2, which does not have any layers, the characteristics are improved, and for the sum Jrv 0 gas composition, CH, / S i H, = 0.1 to 2.
The effect was observed between 4 and 4. The times shown here.

, if too much is introduced, a high resistance layer will be created at the heterojunction interface. D, 'l'! On the contrary, the properties deteriorated, and when the length was too short or the amount introduced was too small, the intermediate layer 5 could not become a layer sufficient to alleviate the lattice mismatch, and no improvement in properties was observed. Furthermore, when the first layer 3 is formed while introducing a small amount of hydrocarbon, the photoconductivity of the first layer 3 is reduced, which only results in a reduction in the conversion efficiency. Table 3 shows a comparison between a photovoltaic device with an intermediate layer and a device without it, and it is clear that forming the intermediate layer 5 clearly improves each characteristic factor (Voc, Jsc, FF). , it has become possible to sufficiently alleviate lattice mismatch and greatly improve device characteristics.

Table 3 The improvement effect of this intermediate layer is as shown in FIG. 4, when a transparent conductive film 6, a-
8iC:H 9 layer 4, a-8i:H lin layer 3a-8
i: HO) Even when laminating the n-layer 2 and the metal electrode 9, if a small amount of hydrocarbon is introduced between the n-layer 4 and the n-layer 3 to form the intermediate layer 5, the intermediate layer shown in FIG. Similar improvements in properties were achieved compared to devices with conventional structures without layers. A similar effect of the intermediate layer was also observed when an n-type a-8iC:H film was used as the window layer.

Furthermore, not only a-8iC:H/a-8i:H(7) heterojunction, but also NH3 gas or N2 gas in the raw material gas.
Nitrogen addition a-8i and a-8i:H formed by adding gas
In the heterojunction of It was discovered that a heterojunction can be formed without deteriorating the bonding properties by providing a lattice mismatch at the bonding interface.

〔Effect of the invention〕

The present invention is based on chemical 4 (a layer in which the first layer is located between the two layers) in order to alleviate the lattice mismatch of the interojunction formed between two layers of a semiconductor thin film. Characteristics deteriorated due to lattice mismatch are recovered, a heterojunction semiconductor device with good characteristics can be formed, and the characteristics of a photovoltaic element with a window layer supporting an a-8iC:n layer with good optical transparency are improved. can be applied very effectively to

[Brief explanation of the drawing]

Figure 1 is a sectional view of an embodiment of the present invention, Figure 2 is a sectional view of a conventional example before its improvement, Figure 3 is a relationship diagram between photoelectric conversion efficiency and intermediate layer film thickness, and Figure 4 is a diagram showing the relationship between photoelectric conversion efficiency and intermediate layer film thickness. FIG. 5 is a cross-sectional view of another embodiment of the present invention, and FIG. 5 is a cross-sectional view of the conventional example before its improvement. 2-...a-8i: H* n layer, 3...a-8i:
H111 layer, 4...a-8iC:Hφp layer, 5...
middle class. Takeuchi, Hara Kotakawa 1) Nekibe

Claims (1)

[Claims] 1) In a device having a heterojunction formed by two semiconductor layers with different bandgaps, a semiconductor layer whose chemical composition is intermediate between the chemical compositions of the semiconductors in both layers is placed between the amphibodiconductor layers. intervene