Signal generation in a hydrogenerated amorphous silicon detector

The signals produced in thick hydrogenated amorphous silicon p-i-n detectors were measured using incident light pulses with different mean free paths. The signal shapes as a function of bias potential were analyzed in terms of the mobilities and mean free paths of the electrons and holes. The latter were measured by transient photoconductivity methods using a pulsed nitrogen-dye laser system. Measurements on relatively thick samples of a-Si:H show ionized dangling bond densities in the range of 6-70×10¹⁴ cm^-3. While the electron mobility increases by ~20% at high field, hole mobility increases by ~40% from the low-field values. This increase in mobility is attributed to dispersion of the transport, but there may be a Poole-Frenkel effect involving the nondispersive electrons