Microcrystalline silicon phase in silicon oxide thin films developed by photo-CVD technique

Intrinsic and p-type muc-Si/a-SiOx:H films have been developed by photochem ical vapor deposition using SiH4, CO2, B2H6 and H-2 gases. The level of bor on doping [f = B2H6/(SiH4 + CO2)] and hydrogen dilution [y = H-2/(SiH4 + CO 2)] significantly affected the structural and optoelectronic properties of the material. The effect of chamber pressure was also studied. The crystall ine planes of silicon were identified by X-ray diffraction and transmission electron microscopy. No evidence of crystalline silicon oxide was observed , i.e. oxygen incorporation occurred only in the amorphous phase. The fract ion of crystallinity in the films was calculated from Raman spectra. Boron incorporation increased the conductivity, but beyond a certain level it dec reased due to deterioration in the crystallinity. By the optimization of de position parameters, high conducting (2.2 x 10(-1) Scm(-l)) p-type microcry stalline silicon-oxygen alloy films were developed for an optical gap (E-04 ) of 1.95 eV. This would be useful for a window layer or the tunnel junctio n of solar cell. (C) 2000 Elsevier Science S.A. All rights reserved.