The effect of the undoped GaN/buffer-layer interface on the operation of Schottky diodes and MESFET devices

Abstract The effect of the interfacial region lying in between undoped GaN (u-GaN) and the buffer-layer on the forward current properties of lateral-type GaN Schottky diodes and planner GaN metal-semiconductor-field-effect-transistors (MESFETs) grown on sapphire substrates has been investigated. Experimental results have revealed higher current densities for devices grown on patterned sapphire substrates (PSS) compared to flat sapphire substrates (FSS) owing to the different carrier transport properties of the interfacial regions. Simulations using the charge transport model showed a good agreement with the experimental results. It is disclosed that the interfacial region is acting as channel in which the current passes in between the device metallic contacts. Owing to the presence of the interfacial regions, the lateral Schottky diodes exhibit high current densities but without change in their on-state-voltage, whereas the planar MESFETs could hardly reach cut-off or show saturation behavior. Studying the effect of the interfacial region on the operation of GaN power devices would help in optimizing the device design and efficiency, and further facilitate their monolithic integration with GaN-based LEDs.