a-Si:H films deposited at high rates in a ´VHF´ silane plasma: potential for low-cost solar cells

The very-high-frequency glow discharge (VHF-GD) is a high-rate deposition method for amorphous silicon based on the use of plasma excitation frequencies in the range 30-150 MHz. Thereby the high-energy tail of the electron energy density function is enhanced, increasing the deposition rate R, without a corresponding increase in electric field and ion bombardment. An extensive set of optoelectronic properties ( sigma _dark, E_a, sigma p_h, CPM, PDS, TOF, SSPG, steady-state Hecht plot) is presented for samples prepared by VHF-GD for the above frequency range and R approximately=12-15 AA/s. Emphasized are hole transport properties. With values of ( mu ^D tau ^t)_h by TOF (time of flight) around 3*10^-10 but up to approximately=5*10^-9 cm²/V, VHF-GD is judged to be adequate for solar-cell applications.