First demonstration of GaN-based vertical nanowire FET with top-down approach

GaN-based field effect transistors (FETs) are widely used in power switching and amplifier application due to its superior material properties such as wide band-gap energy, high breakdown field, and high electron saturation velocity, which results in high output current and high breakdown voltage [1]. On the other hand, nanowire transistors are extensively investigated to improve device performance such as fin-shaped FETs (FinFETs), lateral and vertical type nanowire FETs [2 - 4]. Especially, vertical nanowire FETs (VNFETs) are currently being evaluated as a promising device technology due to its negligible trapping and leakage from the buffer layer, wrap-gated structure and possibility of very short gate length (below 20 nm). VNFETs using Si, InAs and InGaAs materials were already introduced. However, GaN-based VNFETs have been never fabricated due to difficulty in obtaining vertical nanowire structure with high aspect ratio and their complex fabrication process. In this work, we fabricated the GaN-based VNFET, for the first time, by combining conventional e-beam lithography and dry etching technique with strong anisotropic TMAH wet etching.