Magneto-optical properties of Cr3+ in beta-Ga2O3

Abstract

beta-Ga2O3 is a wide bandgap semiconductor that is attractive for various applications, including power electronics and transparent conductive electrodes. Its properties can be strongly affected by transition metal impurities commonly present during the growth such as Cr. In this Letter, we determine the electronic structure of Cr3+ by performing a correlative study of magneto-photoluminescence (magneto-PL) and electron paramagnetic resonance. We unambiguously prove that the so-called R-1 and R-2 PL lines at around 1.79eV originate from an internal transition between the first excited state (E-2) and the (4)A(2) ground state of Cr3+. The center is concluded to have monoclinic local symmetry and exhibits a large zero-field splitting (similar to 147 mu eV) of the ground state, which can be directly measured from the fine structure of the R1 transition. Furthermore, g-values of the first excited state are accurately determined as g(a) = 1.7, g(b) = 1.5, and g(c*) = 2.1. Our results advance our understanding of the electronic structure of Cr in beta-Ga2O3 and provide a spectroscopic signature of this common residual impurity. (C) 2021 Author(s). ; Funding Agencies|Linkoping University; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Interaction of Ionizing Radiation with Matter University Research Alliance (IIRM-URA) - Department of the Defense, Defense Threat Reduction Agency [HDTRA1-20-2-0002]; NSF DMRNational Science Foundation (NSF) [1856662]