Record thick $\kappa(\varepsilon)$-Ga$_2$O$_3$ epitaxial layers grown on GaN/$c$-sapphire

Record thick (up to 100 $\mu$m) epitaxial layers of a prospective metastable semiconductor Ga$_2$O$_3$ were grown by HVPE (Halide Vapor Phase Epitaxy) on GaN buffer layers on c-sapphire substrates. The X-ray diffraction pattern of the layers show that the structure of the layer is a pure $\kappa(\varepsilon)$-Ga$_2$O$_3$ without any other phases. At the same time, the organization of a domain structure was observed, which manifests itself in the form of pseudohexagonal prisms that retain the orientation of the gallium nitride sublayer. Schottky diodes with nickel contacts were fabricated and the electrical and photoelectric properties of the layers were studied. Capacitance-voltage ($C$–$V$) and frequency- capacitance ($C$–$f$) dependencies were studied, photocurrent and photocapacitance spectra were measured.