Charge transport through α-monoclinic selenium

The existence of surface barriers on α-monoclinic selenium crystals has been demonstrated. Photometric measurements indicate electron barrier energies of 1.05 and 1.3 eV, respectively, for Ga and Au contacts. The mobilities of holes and electrons have been measured by a time-of-flight technique to be about 0.2cm^2/Vsec and 1.6cm^2/Vsec, respectively, at room temperature. The hole mobility was found to be limited by traps 0·23 ± 0.01 eV above the valence levels, while the electron mobility is an intrinsic mobility limited by scattering. It was found that in the region of low carrier density (i.e. no space charge effects) the collection efficiency was limited by diffusion of carriers into the metal contact