Impurity and defect passivation in poly-Si films fabricated by aluminium-induced crystallisation

Data from resistivity, optical transmission and reflectance, and open-circuit voltage (V/sub oc/) measurements show hydrogen or ammonia plasma treatment greatly reduces the effective doping concentration, the parasitic optical absorption and improves the minority carrier properties of poly-Si films fabricated by aluminium-induced crystallisation (AIC) on glass substrates. Two 450 nm thick AIC poly-Si films on glass, one hydrogenated and one non-hydrogenated, were used to fabricate poly-Si/a-Si:H heterojunctions. The non-hydrogenated sample had a 1-sun V/sub oc/ of 136 mV and the hydrogenated sample had a 1-sun V/sub oc/ of 236 mV. The poor V/sub oc/ indicates that AIC poly-Si films are more suitable as seed layers than as absorber layers. However, heterojunctions are sensitive to surface conditions and thus further V/sub oc/ improvements may be possible by surface optimization of the hydrogenated AIC poly-Si film prior to the formation of the heterojunction.