Dual Nature Acceptors in Semiconductors: Small Polarons versus Shallow States in Gallium Nitride

Currently, only one shallow acceptor (Mg) has been discovered in GaN. Here, using photoluminescence (PL) measurements combined with hybrid density functional theory, we demonstrate that a shallow state also exists for the Be Ga acceptor level at 113 meV above the valence band, which is the lowest value among dopants in GaN reported to date. Calculations suggest that the BeGa is a dual-nature acceptor with a shallow state and a strongly localized small polaronic state with a significantly lower hole capture efficiency. Using theoretical calculations in comparison with experimental PL measurements, we find several dual nature defects in GaN. The physics of defects in semiconductors, theoretical approaches, experimental techniques, and the search for p-type wide band gap semiconductors are discussed in this talk. 

Speaker bio: Denis Demchenko, Ph.D., is a professor in the Department of Physics at Virginia Commonwealth University.