Ultralow surface recombination in p-Si passivated by catalytic-chemical vapor deposited alumina films

The passivation effects of AlOx films were investigated for p-type crystalline Si (c-Si) solar cells. The AlOx films were deposited on 10 Ωcm c-Si substrates by catalytic chemical vapor deposition (Cat-CVD) using tri-methyl aluminum (TMA) and O2 at a film temperature of 230 °C. The surface recombination velocity (S0) at the AlOx/Si interface was measured to be below 0.5 cm/s for AlOx films deposited with O2/TMA gas flow-rate ratios of 15–35. This ultra low S0 was achieved primarily by band bending due to the negative interface fixed-charge density (Nf) of an order of 1012 charges/cm2. The decrease in interface trapping density Dit in the negative fixed charge region assists in decreasing S0.