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

• Published in: Physical review letters Vol. 126; no. 2; p. 027401
• Main Authors: Demchenko, D O, Vorobiov, M, Andrieiev, O, Myers, T H, Reshchikov, M A
• Format: Journal Article
• Language: English
• Published: United States American Physical Society 15-01-2021
• Subjects: Beryllium; Density functional theory; Photoluminescence; Valence band
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.126.027401

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.