Investigation of top gate GaN thin-film transistor fabricated by DC magnetron sputtering

Abstract

Top-gate thin-film transistors (TFTs) with an n-type GaN thin film active channel layer have been fabricated and characterized. At a substrate temperature of 550 °C, rather than room temperature, the GaN thin films deposited by the reactive direct current magnetron sputtering technique have an average grain size of 25 nm. Without high temperature postannealing process, the proposed GaN TFTs exhibit good electrical performance with a field effect mobility of 2.5 cm2/V s, a threshold voltage of 4.5 V, an on/off current ratio of 1.5 × 105, and a subthreshold swing of 0.7 V/decade. The proposed GaN thin film is promising for TFT active channel application in active-matrix display.