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Shallow and Deep States of Beryllium Acceptor in GaN: Why Photoluminescence Experiments Do Not Reveal Small Polarons
D O Demchenko1, M Vorobiov1, O Andrieiev1
1Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23220, USA.
Abstract:
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 effective-mass state also exists for the Be_{Ga} acceptor. A PL band with a maximum at 3.38 eV reveals a shallow Be_{Ga} acceptor level at 113±5 meV above the valence band, which is the lowest value among any dopants in GaN reported to date. Calculations suggest that the Be_{Ga} is a dual-nature acceptor with the "bright" shallow state responsible for the 3.38 eV PL band, and the "dark," strongly localized small polaronic state with a significantly lower hole capture efficiency.
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