40 Years Trajectory of Amorphous Semiconductor Research
- PDF / 3,776,091 Bytes
- 13 Pages / 612 x 792 pts (letter) Page_size
- 21 Downloads / 200 Views
40 Years Trajectory of Amorphous Semiconductor Research Yoshihiro Hamakawa Faculty of Science and Engineering, Ritsumeikan University 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan ABSTRACT A review is given on a research trajectory of amorphous and microcrystalline semiconductors and their device applications proceeded since 1970. A brief explanation on the motivation to start amorphous semiconductor research is given to produce a new kind of synthetic semiconductor having continuous energy gap controllability with valency electron controllability through our experience of modulation spectroscopy in semiconductors. The first material we have challenged is Si-As-Te chalcogenide semiconductor which has a very wide vitreous region in Gibb's Triangle. A series of systematic experiments has been carried out in the terrestrial environment since 1971, and also within the TT-500A rocket experiment in 1980, and the Spacelab. J experiments FMPT (First Material Processing Test) project in 1992. The second material is hydrogenated amorphous silicon (a-Si:H) and its alloys started in 1976 just after the Garmisch Partenkirchen ICALS-6. With some basic research on the a-Si:H film deposition technology and film quality improvement, our continuous effort to improve the efficiency bore the tandem type solar cells in 1979, and also new products of a-SiC:H and a-SiGe:H in the early period of 1980s are described. These innovative device structures and materials have bloomed in the middle of 1980s in R & D phase such as a-SiC/a-Si heterojunction solar cells, a-Si/a-SiGe and also a-Si/poly-Si tandem type solar cells, and industrialized in recent few years. New kind of trials on full-color thin film light emitting devices has also been recently initiated with wide range of band gap controllability of a-SiC:H. The third material is microcrystalline silicon (µc-Si) and their alloys which gathers a tremendous R & D effort as a promised candidate for the bottom cell of the a-Si/µc-Si tandem solar cells aimed for the all-round plasma CVD process for the next age thin film photovoltaic devices. In the final part of presentation, a brief discussion will be given on a technological evolution from "bulk crystalline age" to "multilayered thin film age" in the semiconductor optoelectronics toward 21 century . FABRICATION OF SYNTHETIC SEMICONDUCTORS – BAND GAP CONTROL AND VALENCY ELECTRON CONTROL – In the last half period of 1960s, we had conducted research on band structure characterization of various semiconductors by the modulation spectroscopy, and also been interested in an electronic activity of lattice defects in semiconductors. On that time, many varieties of new semiconductors such as III-V, II-VI and chalcopyrite compound semiconductors were produced, and their band gap parameters are characterized by our laboratory. Through these investigations, I have had a dream to control the band gap parameters in semiconductors. The dream becomes a strong motivation to start amorphous semiconductor research, that is, production of a new kind of sy
Data Loading...
