Improved Passivation of a-Si:H / c-Si Interfaces Through Film Restructuring

The as-deposited passivation quality of amorphous silicon films on crystalline silicon surfaces is dependent on deposition conditions and resulting hydrogen bonding structure. However the initial surface passivation can be significantly improved by low temperature post-deposition anneal. For example an improvement in effective lifetime from 780 mu sec as-deposited to 2080 mu sec post-anneal is reported in the present work. This work probes the hydrogen bonding environment using monolayer resolution Brewster angle transmission Fourier transform infrared spectroscopy of 100 angstrom thick films. It is found that there is significant restructuring at the a-Si:H / c-Si interface upon annealing and a gain of mono-hydride bonding at the c-Si surface is detected. Calculations show an additional 3.56 - 4.50 x 10(14) cm(-2) mono-hydride bonding at c-Si surface due to annealing. The estimation of the surface hydride oscillator strength in transmission mode is reported for the first time to be 7.2 x 10(-18) cm on Si (100) surface and 7.5 x 10(-18) cm on Si (111).