Vertical architecture for enhancement mode power transistors based on GaN nanowires

The demonstration of vertical GaN wrap-around gated field-effect transistors using GaN nanowires is reported. The nanowires with smooth a-plane sidewalls have hexagonal geometry made by top-down etching. A 7-nanowire transistor exhibits enhancement mode operation with threshold voltage of 1.2 V, on/off current ratio as high as 10⁸, and subthreshold slope as small as 68 mV/dec. Although there is space charge limited current behavior at small source-drain voltages (V_ds), the drain current (I_d) and transconductance (g_m) reach up to 314 mA/mm and 125 mS/mm, respectively, when normalized with hexagonal nanowire circumference. The measured breakdown voltage is around 140 V. This vertical approach provides a way to next-generation GaN-based power devices.