An annealing method for switching AlGaN/GaN field effect transistors employing an excimer laser

Abstract

A post-annealing method employing excimer laser pulses is proposed to improve the transfer characteristics and the breakdown voltage of unpassivated AlGaN/GaN heterostructure field-effect transistors (HFETs) for switching devices. XeCl excimer laser pulses with a wavelength of 308 nm anneal the unpassivated AlGaN/GaN HFET after Schottky gate metallization. The interface defects between the Schottky gate metal and the GaN layer are decreased by the lateral heat diffusion of the laser pulses. The temperature of the device during the laser pulse is analysed by the one-dimensional heat diffusion equation. Our experimental results show that the drain current and the maximum transconductance of the AlGaN/GaN HFET after 10 laser pulses are 496 and 134 mS mm−1, while a virgin device shows 434 and 113 mS mm−1, respectively. The measured leakage current of the AlGaN/GaN HFET at VG=−6 V is decreased from 1.95 to 1.53 mA mm−1 after 600 laser pulses. The breakdown voltage of the AlGaN/GaN HFET is increased due to the decreased leakage current.