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

Abstract

Intrinsic and p-type μc-Si/a-SiO x :H films have been developed by photochemical vapor deposition using SiH 4, CO 2, B 2H 6 and H 2 gases. The level of boron doping [ f=B 2H 6/(SiH 4+CO 2)] and hydrogen dilution [ y=H 2/(SiH 4+CO 2)] significantly affected the structural and optoelectronic properties of the material. The effect of chamber pressure was also studied. The crystalline 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 fraction of crystallinity in the films was calculated from Raman spectra. Boron incorporation increased the conductivity, but beyond a certain level it decreased due to deterioration in the crystallinity. By the optimization of deposition parameters, high conducting (2.2×10 −1 Scm −1) p-type microcrystalline 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 junction of solar cell.