Full bandgap defect state characterization of β-Ga₂O₃ grown by metal organic chemical vapor deposition

The results of a detailed investigation of electrically active defects in metal-organic chemical vapor deposition (MOCVD)-grown β-Ga2O3 (010) epitaxial layers are described. A combination of deep level optical spectroscopy (DLOS), deep level transient (thermal) spectroscopy (DLTS), and admittance spectroscopy (AS) is used to quantitatively map the energy levels, cross sections, and concentrations of traps across the entire ∼4.8 eV bandgap. States are observed at EC-0.12 eV by AS; at EC-0.4 eV by DLTS; and at EC-1.2 eV, EC-2.0 eV, and EC-4.4 eV by DLOS. While each of these states have been reported for β-Ga2O3 grown by molecular-beam epitaxy (MBE) and edge-defined film fed grown (EFG), with the exception of the EC-0.4 eV trap, there is both a significantly different distribution in the concentration of these states and an overall ∼10× reduction in the total trap concentration. This reduction is consistent with the high mobility and low background compensating acceptor concentrations that have been reported for MOCVD-grown (010) β-Ga2O3. Here, it is observed that the EC-0.12 eV state dominates the overall trap concentration, in marked contrast with prior studies of EFG and MBE material where the state at EC-4.4 eV has dominated the trap spectrum. This sheds light on possible physical sources for this ubiquitous DLOS feature in β-Ga2O3. The substantial reduction in trap concentration for MOCVD material implies great promise for future high performance MOCVD-grown β-Ga2O3 devices.