Effect of sputtering time and RF power on the current voltage characteristics of amorphous (undoped) silicon films deposited on crystalline silicon by RF sputtering

The samples A, B, C, D, E, and F were fabricated, depositing films of amorphous silicon (a-Si) by RF Sputtering on p-type crystalline silicon (c-Si) substrates, besides the control sample M/S which was free of a-Si. Ohmic contacts to c-Si substrates were obtained by sputter deposition of Al, followed by 15 min. annealing at 500°C. Top Ni contacts were prepared by thermal deposition. The room temperature current-voltage (I-V) characteristics of all the samples were measured in the range from -10 V to +10 V. The experimental data was described by a relation of the form JαV^m with 0.5<m<26 under reverse bias and 1.5<m<5.7 under forward bias. In the region with m≫2, the I-V data also fitted well to Schottky equation which permitted the determination of barrier heights