Photoluminescence microscopy as a noninvasive characterization method for defects in gallium oxide and aluminum gallium oxide epitaxial films

Herein we utilize polarized photoluminescence (PL) microscopy and spectral analysis to locate and characterize many different types of pm-scale extended defects present in melt -grown bulk crystals and metal-organic vapor-phase epitaxy (MOVPE)-grown epitaxial thin films of 13-Ga2O3 and 13-(Al,Ga)2O3. These include pits, divots, mounds, scratches, rotation domain boundaries, stacking faults, cracks, and other defect categories. Some types of pm-scale defects simply decrease overall PL yield, while others emit different spectra than single crystal regions. We combine PL microscopy with atomic force microscopy (AFM) and scanning electron microscopy (SEM) to provide detailed characteristics of these different types of features which can arise from both bulk crystal growth, surface preparation, and epitaxial growth processes. We show that sample quality (in terms of extended defects) can be determined by using PL and that attributing spectral features to isolated point defects is invalid unless the sample is proven to not contain extended defects.