High-Quality AlGaN/GaN HEMTs Growth on Silicon Using Al0.07Ga0.93N as Interlayer for High RF Applications

Abstract

In this study, AlGaN/GaN high electron mobility transistor (HEMT) with different interlayer thicknesses of Al0.07Ga0.93N were grown by metal-organic chemical vapour deposition (MOCVD) is investigated. The AlGaN/GaN HEMTs have the same device’s structure, with the Al0.07Ga0.93N interlayer thickness varied from 0 to 800 nm. All of the samples demonstrate high crystal quality in the GaN channel, with low dislocation density of (1.34–3.81) × 109 cm−2 and low AFM surface roughness of 0.27–0.39 nm. The heterostructure with an interlayer exhibits better mobility (1750 cm2 V∙s−1) compared to the structure without an interlayer (1610 cm2 V∙s−1). Furthermore, the interlayer improves breakdown voltage, and reduces insertion loss. The DC characteristics show that the 300 nm-thick Al0.07Ga0.93N is beneficial in improving leakage current and iso-breakdown voltage up to 450 V at a spacing of 10 μm. The insertion loss reduces to –0.75 dB mm−1 compared to the structure without an interlayer. The device with a 300 nm-thick Al0.07Ga0.93N interlayer exhibits the potential of RF, including a measured transconductance of 440 mS∙mm−1 and cutoff frequencies of f T / f max = 48/96 GHz at a given bias point.