Structural and electrical properties of thick κ-Ga2O3 grown on GaN/sapphire templates

Thick (23 mu m) films of kappa-Ga2O3 were grown by Halide Vapor Phase Epitaxy (HVPE) on GaN/sapphire templates at 630 & DEG;C. X-ray analysis confirmed the formation of single-phase kappa-Ga2O3 with half-widths of the high-resolution x-ray diffraction (004), (006), and (008) symmetric reflections of 4.5 arc min and asymmetric (027) reflection of 14 arc min. Orthorhombic kappa-Ga2O3 polymorph formation was confirmed from analysis of the Kikuchi diffraction pattern in electron backscattering diffraction. Secondary electron imaging indicated a reasonably flat surface morphology with a few (area density & SIM;10(3) cm(-2)) approximately circular (diameter & SIM;50-100 mu m) uncoalesced regions, containing kappa-Ga2O3 columns with in-plane dimensions and a height of about 10 mu m. Micro-cathodoluminescence (MCL) spectra showed a wide 2-3.5 eV band that could be deconvoluted into narrower bands peaked at 2.59, 2.66, 2.86, and 3.12 eV. Ni Schottky diodes prepared on the films showed good rectification but a high series resistance. The films had a thin near-surface region dominated by E-c - 0.7 eV deep centers and a deeper region (& SIM;2 mu m from the surface) dominated by shallow donors with concentrations of & LE;10(16) cm(-3). Photocurrent and photocapacitance spectra showed the presence of deep compensating acceptors with optical ionization energies of & SIM;1.35 and 2.3 eV, the latter being close to the energy of one of the MCL bands. Deep level transient spectroscopy revealed deep traps with energies near 0.3, 0.6, 0.7, 0.8, and 1 eV from the conduction band edge. The results show the potential of HVPE to grow very thick kappa-Ga2O3 on GaN/sapphire templates. (C)2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/)

Automated summary

Thick films (23 μm) of kappa-Ga2O3 were successfully grown on GaN/sapphire templates using Halide Vapor Phase Epitaxy (HVPE). The films exhibited good crystalline quality and surface morphology. They possessed specific properties such as a wide absorption band and deep-level traps.