Electronic Processes in α-Sulfur

Abstract

The mobilities of photo-generated electrons and holes in orthorhombic sulfur are determined by drift mobility techniques. At room temperature electron mobilities between 0.4 cm^2/V-sec and 4.8 xm^2/V-sec and hole mobilities of about 5.0 cm^2/V-sec are reported. The temperature dependence of the electron mobility is attributed to a level of traps whose effective depth is about 0.12 eV. This value is further supported by both the voltage dependence of the space-charge-limited, d.c. photocurrents and the photocurrent versus photon energy measurements. As the field is increased from 10kV/cm to 30kV/cm a second mechanism for electron transport becomes appreciable and eventually dominates. Evidence that this is due to impurity band conduction at an appreciably lower mobility (4.10^(-4) cm^2/V-sec) is presented. No low mobility hole current could be detected for fields below 35 KV/cm. When fields exceeding 30 kV/cm for electron transport and 35 kV/cm for hole transport are applied, avalanche phenomena are observed. The results obtained are consistent with recent energy gap studies in sulfur. The theory of the transport of photo-generated carriers is modified to include the case of appreciable thermo-regeneration from the traps in one transit time.

Additional details