Study of gap states in hydrogenated amorphous silicon by transient and steady-state photoconductivity measurements

The energy distribution of gap states in amorphous hydrogenated silicon has been investigated by transient photoconductivity (TPC) and steady-state photoconductivity (SPC) measurements. Both TPC and SPC measurements show that the shallow states decrease exponentially with energy away from the conduction-band edge with a characteristic temperature of 300 K whereas the deep states decrease with a characteristic temperature of about 1000 K. The transition energy is located around 0.3 eV from the conduction-band edge. The density of states at the Fermi level was obtained from frequency dependence of the capacitance (C-ω curve) of Schottky diodes. The derived density-of-states distribution as obtained from TPC, SPC, and C-ω measurements agrees with results obtained from field-effect and C-V measurements.