Temperature dependence of electronic bands in Al/GaN by utilization of invariant deep defect transition energies

We show experimentally that deep point defect levels in GaN, AlN, and AlGaN are constant with respect to the vacuum level and can be used as invariant internal energy references. This offered a convenient and quick way to assess band shifts and impurity levels as a function of temperature via photoluminescence. For AlGaN, we determined that the band shift in the temperature range of 3-600 K occurred primarily in the valence band and that the lowering of the conduction band edge was comparatively small. The valence band shift (as a fraction of the Varshni bandgap shift) in AlGaN varies from similar to 70% in AlN to similar to 90% in GaN. Published under an exclusive license by AIP Publishing.

Automated summary

The experiment showed that deep point defect levels in GaN, AlN, and AlGaN remain constant with respect to the vacuum level, serving as invariant internal energy references. This allows for a convenient way to assess band shifts and impurity levels as temperature changes through photoluminescence. In AlGaN, it was found that the band shift is primarily in the valence band, with a relatively small change in the conduction band edge.