Optical properties of mist CVD grown <i>κ</i>-Ga<sub>2</sub>O<sub>3</sub>
Usman Ul Muazzam, Prasad S Chavan, R. Muralidharan, Srinivasan Raghavan, Digbijoy N. Nath
Abstract
Abstract We report on the growth of crystalline κ -Ga 2 O 3 using mist-chemical vapor deposition (CVD) on (0001) sapphire. The κ -phase was confirmed using high-resolution x-ray diffraction (XRD) θ -2 θ 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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">Φ</mml:mi> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) and ideality factor ( η ), which were found to be correlated with temperature. Photodetectors fabricated on the sample exhibited pure solar-blind characteristics.