Optical properties of mist CVD grown kappa-Ga2O3

We report on the growth of crystalline kappa-Ga2O3 using mist-chemical vapor deposition (CVD) on (0001) sapphire. The kappa-phase was confirmed using high-resolution x-ray diffraction (XRD) theta-2 theta scan and pole figure-scan of (122) reflex, respectively, while an on-axis full width at half maximum (FWHM) of 104 arcsec was measured in symmetric rocking curve scan. Further, the heteroepitaxial film was analyzed using a mosaic crystal model employing reciprocal space maps (RSM) and a series of asymmetric rocking curve scans. A bandgap of 5.1 eV and excitonic binding energy of 85 meV were estimated from absorption measurements. Built-in field, depletion width, and doping density level were extracted from parabolic WKB model fit. Cathodoluminescence (CL) spectroscopy revealed a defect peak at 329 nm, which was found to be blue-shift with increasing excitation energy, indicating a possible donor-acceptor pair (DAP) transition. Temperature-dependent Current-voltage (I-V) study was performed to extract Schottky barrier height (Phi(B)) and ideality factor (eta), which were found to be correlated with temperature. Photodetectors fabricated on the sample exhibited pure solar-blind characteristics.