Investigations of compensating deep acceptor defects in β-Ga₂O₃ by thermal and optical defect spectroscopy methods

Compensating deep level defect states that influence the electrical properties of β-phase gallium oxide (β-Ga₂O₃) can be introduced intentionally through doping, or unintentionally through unwanted impurities and intrinsic defects. Understanding the complex behavior of these compensating centers is essential for optimizing β-Ga₂O₃ for both high voltage and RF electronics. Applications in harsh environments, such as in space, add further complications due to defect creation resulting from high energy irradiation. Due to its inherent n-type conductivity, compensating deep acceptor states intentionally introduced by doping with Nitrogen, Iron or Magnesium to create semi-insulating regions of device structures are of great interest. However, inadvertent impurities such as Carbon are also predicted to create deep acceptors and can be problematic. The presence of intrinsic defects that form during growth or introduced by harsh environments makes the understanding of how defects impact material and device properties very complex. Here we use deep level transient (thermal) spectroscopy (DLTS) and deep level optical spectroscopy (DLOS) to identify, compare and characterize individual deep acceptor states created by both extrinsic and intrinsic sources in β-Ga2O3, and compare with theoretical predictions. Compensation efficiencies between acceptor choices are compared, and some of the more unusual behaviors of very deep states present below midgap are described, where both conduction and valence band transitions are observed and explained. Radiation studies used to differentiate extrinsic from intrinsic sources will be discussed in the context of unraveling the comprehensive impacts of defects in β-Ga2O3.