Growth and Characteristics of n-VO2/p-GaN based Heterojunctions

Abstract

n-VO2/p-GaN based oxide-nitride heterojunctions were realized by growing high quality VO2 films with precisely controlled thickness on p-GaN/sapphire substrates by oxide molecular beam epitaxy (O-MBE). The high crystalline quality of the n-VO2/p-GaN heterojunctions were confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The phase transition characteristics of the as-grown n-VO2/p-GaN heterojunctions were systematically investigated by temperature-dependent resistivity and infrared transmittance measurements. The results indicated that an excellent reversible metal-to-insulator (MIT) transition is observed with an abrupt change in both resistivity and infrared transmittance (IR) at 330 K, which was lower than the 341 K for bulk single crystal VO2. Remarkably, the resistivity-temperature curve was well consistent with that obtained from the temperature dependent IR transmittance. Meanwhile, the current-voltage characteristics originated from the n-VO2/p-GaN interface were demonstrated both before and after MIT of VO2 overlayer, which were attributed to the p-n junction behavior and Schottky contact character, respectively. The design and modulation of the n-VO2/p-GaN based heterostructure devices will benefit significantly from these achievements.