Indium defect complexes in (In x Ga1−x )2O3: a combined experimental and hybrid density functional theory study

Abstract

Indium defects in small concentration (In x Ga1−x )2O3 were studied using a combination of spectroscopic and magnetic measurements on thin films varying the indium concentration, coupled with hybrid density functional theory simulations using the supercell method. X-ray diffraction spectra along with Tauc plots and density of states plots reveal a decrease (increase) in the electronic band gap (interlayer lattice spacing) due to the inclusion of indium in monoclinic Ga2O3, while room-temperature Hall measurements show an increase in n-type conductivity. Formation energy calculations reveal that the defect complex of substitutional indium at the octahedrally coordinated cation site (InGa) coupled with an indium interstitial (Ini) in the largest Ga–O cavity in the bulk (ia ), where the two impurities are a maximal distance away in the unit cell, results in the lowest formation energy across much of the electronic band gap; near the conduction band edge the single InGa defect becomes the lowest energy defect, though. These calculations help shed light on the impurity band enhanced, n-type conductivity increase due to small concentration indium doping in Ga2O3 as seen in the spectroscopic/magnetic measurements.