TRANSIENT PHOTOCURRENT STUDIES ON AMORPHOUS AND BETA-RHOMBOHEDRAL BORON

摘要

Carrier transport properties in amorphous and beta-rhombohedral boron were studied by the time of flight method. The activation energy for holes in beta-rhombohedral boron was estimated to be 240 meV. This activation energy corresponds to the depth of hole traps originating from B-12, that is, the intrinsic acceptor level. Dispersive (non-Gaussian) transient photocurrents were observed both for electrons and holes in amorphous boron. The activation energy for electrons and holes were estimated to be about 20 and 85 meV, respectively. The average hopping distance of holes was evaluated from the electric field dependence of the photocurrent to be 11 Angstrom. These activation energies and hopping distances are small compared with those of other amorphous semiconductors. The results suggest that the excited carriers propagate by hopping between localized states within a certain narrow band. (C) 1997 Academic Press. [References: 12]