Shallow and Deep States of Beryllium Acceptor in GaN: Why Photoluminescence Experiments Do Not Reveal Small Polarons for Defects in Semiconductors

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 BeGa 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 BeGa 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.

Automated summary

By using photoluminescence measurements and hybrid density functional theory, researchers have found a shallow effective mass state for the Be-Ga acceptor in GaN, with a level at 113 +/- 5 meV above the valence band. Calculations indicate that the BeGa acceptor has a bright shallow state responsible for the 3.38 eV PL band, as well as a dark, strongly localized small polaronic state with a lower hole capture efficiency.