Deposition of Narrow Bandgap Amorphous Semiconductor for High Efficiendy Solar Cells

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During 1991-1992 academic years, the following results are obtained from the research on deposition of high-qualty a-Ge : H by ECR plasma.1.Irradiation of atomic hydrogen together with adequate ion flux on growth surface in ECR PCVD with a low flow rate of germane improves optoelectronic properties of a-Ge : H.Any increase in atomic hydrogen irradiation does not cause microcrystallization of the films. The effect is attributable to hydrogen etching from decrease in growth rate.2. Electron-irradiation onto the growth of films promotes an amorphous to microcrystalline phase transition. The transition is enhanced by electron-induced Ge etching. A moderate electron-irradiation together with ion-irradiation significantly improves optoelectronic properties of a-Ge : H films.3. Microcrystallization in the three different conditions of silane PCVD ; high gydrogen-dilution, high power and positively biasing is also observed in ECR PCVD of a-Ge : H and attributed to the electron-induced microcrystallization.4.Film quality of a-Ge : H produced by ECR PCVD depends on FWHM of frequency spectrum of microwave power source. A decrease in the FWHM by 1/30 increases optoelectronic properties by two and also improves photoluminesence properties.5.CPM characterization developed for a-Ge : H films gives defects density of order of 10^<16>/cm^3 in a-Ge : H, being comparable to that of device-quality a-Si : H.6.Further investigation should be made to clarify the presence of Staebler-Wronski effect in these high-quality a-Ge : H films.