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. Here, an extensive set of optoelectronic properties (σ_dark, E_a, σ_ph, CPM, PDS, TOF, SSPG, steady-state Hecht plot) is presented for samples prepared by VHF-GD for the above frequency range and R≈12-15 AA/s. Emphasized are hole transport properties. With values of (μ^Dτ^t)_h by TOF (time of flight) around 3*10^-10 but up to ≈5*10^-9 cm²V^-1, VHF-GD is judged to be adequate for solar-cell applications.