Combining steady-state photo-capacitance spectra with first-principles calculations: the case of Fe and Ti in β-Ga2O3

Abstract

In this study, we demonstrate an approach to identify defects in wide band gap semiconductors by comparing accumulatively-recorded derivative steady-state photo-capacitance (SSPC) spectra to simulations using results from first-principles calculations. Specifically, we present a method to simulate SSPC spectra which adopts inputs both from first-principles calculations and the experimental conditions. The applicability of the developed method is demonstrated using the cases of subsitutional Fe (Fe _Ga ) and Ti (Ti _Ga ) defects in β-Ga _2 O _3 . Using deep-level transient spectroscopy, we identify defect levels associated with ${\mathrm{Fe}}_{\text{GaI}}^{0/-}$ ( E _A = 0.66 eV), ${\mathrm{Fe}}_{\text{GaII}}^{0/-}$ ( E _A = 0.79 eV) and ${\mathrm{Ti}}_{\text{GaII}}^{+/\mathrm{0}}$ ( E _A = 1.03 eV) in the β-Ga _2 O _3 samples studied here. Accumulatively-recorded SSPC spectra reveal several defect levels labeled ${T}_{\mathrm{1}}^{\mathrm{E}\mathrm{F}\mathrm{G}}$ – ${T}_{\mathrm{6}}^{\mathrm{E}\mathrm{F}\mathrm{G}}$ with onsets for optical absorption between 1.5 eV and 4.3 eV. The signature ${T}_{\mathrm{1}}^{\mathrm{E}\mathrm{F}\mathrm{G}}$ consists of several overlapping defect signatures, and is identified as being related to ${\mathrm{Fe}}_{\text{GaI}}^{0/-}$ , ${\mathrm{Fe}}_{\text{GaII}}^{0/-}$ and ${\mathrm{Ti}}_{\text{GaII}}^{+/\mathrm{0}}$ by comparing measured and simulated accumulatively-recorded derivative SSPC spectra.

Keywords

• defects in semiconductors
• steady-state photo-capacitance
• first-principles calculations
• β-Ga2O3
• deep-level transient spectroscopy
• wide band gap semiconductors