Determination of trapping centers in beta-rhombohedral boron

Trapping levels and their parameters were studied in high-resistivity, undoped beta-rhombohedral Boron. The study was performed by means of transient photoconductivity, space-charge-limited currents, and thermally stimulated currents. The analysis of the results given by the three methods provides a completely self-consistent model of the trap distribution in energy. A number of specimens were investigated and selfconsistentresults for all samples were found by the three methods. Hole trapping centers deep in the gap are present. In some samples, an exponential distribution starting from 0.36 eV above the valence band was found, together with a discrete shallow (0.02-0.05 eV) level. In other samples, a discrete level at 0.23 eV from the valence band is obsd. Energy traps for electrons are found at ~0.25 eV below the conduction band. The exptl. results are discussed with respect to the transport properties of Boron.