Optimizing GaN structure via high-temperature thermal oxidation for enhanced optical properties

This study investigates the photoluminescence (PL) enhancement in Ga 2 O 3 /GaN heterojunction films fabricated by high-temperature thermal oxidation of unintentionally doped GaN epitaxial wafers. Under 244 nm laser excitation at room temperature, the Ga 2 O 3 /GaN heterojunction exhibits an approximately 1.45-fold augmentation in PL integrated intensity compared to the undoped GaN film. Band structure analysis manifests that the Ga 2 O 3 layer facilitates efficient injection of photo-generated carriers into the GaN layer under 244 nm illumination, thereby amplifying the near-band-edge emission (NBE) of GaN. To further validate this mechanism, P-type GaN (P-GaN) substrates were oxidized to derive Ga 2 O 3 /P-GaN heterojunctions. Under 244 nm excitation, these heterojunction samples exhibit an extraordinary 26-fold PL enhancement. In contrast, no notable PL enhancement is observed under 325 nm laser excitation, confirming the critical role of Ga 2 O 3 in augmenting GaN luminescence, primarily when the excitation photon energy exceeds the bandgap of Ga 2 O 3 . This work presents a novel strategy for optimizing the NBE of GaN.