Influence of growth temperature on defect states throughout the bandgap of MOCVD-grown β -Ga2O3

Abstract

The influence of growth temperature on the distribution (concentrations and energy levels) of individual defect states in metal organic chemical vapor deposition-grown, Si-doped β-Ga2O3 is investigated. A combination of deep level thermal transient/optical spectroscopies and admittance spectroscopy (AS) was used to quantitatively monitor the evolution of trap states throughout the ∼4.8 eV bandgap. States are observed at EC-0.12 eV by AS; at EC-0.4 eV by deep level transient spectroscopy; and at EC-1.2 eV, EC-2.0 eV, and EC-4.4 eV by deep level optical spectroscopy, and showed different dependencies on growth temperatures ranging from 800 °C to 920 °C. The EC-0.4 eV and EC-4.4 eV states both displayed a strong reduction in its concentration with increasing growth temperature, whereas no consistent trends were seen for the states at EC-1.2 eV and 2.0 eV over the temperature range studied. In contrast, the concentration of the EC-0.12 eV trap monotonically increased over the same range of increasing growth temperature, which tracked a slight, monotonic increase in overall Si concentration measured by secondary ion mass spectroscopy with growth temperature. The opposing trends in concentrations for some of these states shifted the dominant deep level in the bandgap from the EC-4.4 eV state at the lowest growth temperature explored here to the EC-0.12 eV state at the highest growth temperature. The shifting dominance of various bandgap states can have important ramifications on β-Ga2O3 device behavior, and the different trends for these deep levels cannot only guide further growth optimization but also advance the identification of their physical sources.