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

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 E_C-0.12 eV by AS; at E_C-0.4 eV by deep level transient spectroscopy; and at E_C-1.2 eV, E_C-2.0 eV, and E_C-4.4 eV by deep level optical spectroscopy, and showed different dependencies on growth temperatures ranging from 800 °C to 920 °C. The E_C-0.4 eV and E_C-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 E_C-1.2 eV and 2.0 eV over the temperature range studied. In contrast, the concentration of the E_C-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 E_C-4.4 eV state at the lowest growth temperature explored here to the E_C-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. [ABSTRACT FROM AUTHOR]