Electronic and optical properties of amorphous Si:H films deposited by chemical vapor deposition

Doping properties, optical absorption, and infrared (IR) spectra of amorphous Si:H(a-Si:H) films prepared by chemical vapor deposition (CVD) of Si2H6 are reported. The optical absorption curves are very sharp and they indicate that the band gap of CVD a-Si:H can be changed substantially by varying the deposition temperature. A band gap of 1.5 eV has been achieved. IR spectra indicate the presence of Si–H and SiH2 bonds, but H content is less than in device-quality glow-discharge deposited a-Si:H. The activation energy of undoped films is 0.6 eV. n-type doping can be achieved by PH3 doping and the activation energy reduces to 0.12 eV upon doping. Photoinduced changes in electron trapping (Staebler–Wronski effect) are small in CVD a-Si:H films.