Transition from amorphous to microcrystalline Si:H: effects of substrate temperature and hydrogen dilution

Abstract Structural changes in silicon films with variations of hydrogen dilution and substrate temperature have been studied. At a critical value of hydrogen dilution in silane (φ) a sharp transition from amorphous to microcrystalline phase has been observed. An increase of substrate temperature from 170 to 340 °C shifts the transition point from φ=95.5% to 93.5%. The change in dark conductivity and absorption corroborate with the change in crystalline volume fraction in the films. The grain size varies from 45 to 360 A depending on deposition conditions. Optical absorption and hydrogen content in the film decreases drastically with formation of microcrystalline structure. Silicon films developed at 340 °C show moderate photosensitivity together with low light induced degradation at low crystallinity, which might be suitable properties for solar cell application.