Physics of Amorphous Silicon–Carbon Alloys

A method for producing an electronic device having a multi-layer structure comprising one or more valence electron controlled semiconductor thin layers formed on a substrate comprises forming at least one of said valence electron controlled semiconductor thin layers controlled according to the plasma CVD method and forming at least one of the other constituent layers according to the method comprising introducing a gaseous starting material for formation of a deposited film and a gaseous halogenic oxidizing agent having the property of oxidizing said starting material into a reaction space to effect chemical contact therebetween to thereby form a plurality of precursors including a precursor in an excited state and transferring at least one of these precursors into a film forming space communicated with the reaction space as a feed source for the constituent element of the deposited film

Method for producing an electronic device having a multi-layer structure

Crystalline semiconductors are very well known, including silicon (the basis of the integrated circuits used in modern electronics), Ge (the material of the first transistor), GaAs and the other III-V compounds (the basis for many light emitters), and CdS (often used as a light sensor). In crystals, the atoms are arranged in near-perfect, regular arrays or lattices. Of course, the lattice must be consistent with the underlying chemical bonding properties of the atoms. For example, a silicon atom forms four covalent bonds to neighboring atoms arranged symmetrically about it. This “tetrahedral” configuration is perfectly maintained in the “diamond” lattice of crystal silicon.

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Amorphous Silicon-Based Solar Cells

Amorphous silicon alloyed p‐i‐n solar cells have been fabricated using a separate chamber photochemical vapor deposition system. The photocharacteristics of such cells have been modestly improved by the addition of a carbon‐alloyed graded‐band‐gap layer at the p(a‐SiC:H)/i(a‐Si:H) heterointerface. The best efficiency obtained for a glass/TCO (transparent conductive oxide)/p(a‐SiC:H)/i(a‐Si:H)/n(μc‐Si:H)/metal structure of this type was 11.2% for a 3×3 mm2 cell; other parameters were Voc=0.882 V, Isc=18.05 mA/cm2, and a fill factor (FF) of 0.702.

Use of a carbon‐alloyed graded‐band‐gap layer at the p/i interface to improve the photocharacteristics of amorphous silicon alloyed p‐i‐n solar cells prepared by photochemical vapor deposition

a‐Si:H films were deposited by direct photochemical vapor deposition using vacuum ultraviolet lights emitted from deuterium (161 nm) and Xe (147 nm) discharge lamps. A source gas of Si2H6 was effectively decomposed, and a high deposition rate of 7.5 nm/min could be achieved in the case of the Xe lamp. The films had excellent electrical and photoelectric properties similar to ordinary films deposited by glow discharge, and showed very little degradation of photoconductivity under illumination.

Deposition of high‐quality a‐Si:H by direct photodecomposition of Si2H6 using vacuum ultraviolet light

Hydrogenated amorphous silicon solar cells were fabricated by photochemical vapor deposition. A three‐separate‐chamber system was newly developed to reduce the contamination of the dopant elements as well as oxygen or water originated by the loading and unloading procedure. Wide optical band‐gap hydrogenated amorphous silicon carbide was prepared using acetylene (C2H2) for the p layer. The deposition conditions for each layer were optimized and the highest‐energy conversion efficiency of 9.64% was obtained. This high conversion efficiency was mainly attributed to the large short‐circuit current which indicated that the quality of the i layer is reasonably good.

H. Takei

Papers

High‐energy conversion efficiency amorphous silicon solar cells by photochemical vapor deposition