AlN/AlGaN heterojunction field-effect transistors with a high-AlN-mole-fraction Al_0.72Ga_0.28N channel grown on single-crystal AlN substrate by metalorganic chemical vapor deposition

Abstract This paper presents research results on AlN/AlGaN heterojunction field-effect transistors (HFETs) with a high-AlN-mole-fraction Al 0.72 Ga 0.28 N channel grown on a single-crystal AlN substrate by metalorganic chemical vapor deposition. Material evaluation results confirmed that the grown AlGaN layer was 100% coherently grown for the underlying AlN substrate and thereby had superior crystal quality as well as the substrate. The fabricated AlGaN-channel HFETs with a gate length of 2 μ m exhibited pinch-off characteristics with the max. current density ( I DS_MAX ) of 21 mA mm −1 , the on-state resistance of 250 Ωmm, the peak transconductance of 4.5 mS mm −1 with the threshold voltage of – 4.6 V, and the on/off ratio of 4 × 10 −5 . The temperature dependence of DC characteristics confirmed that the I DS_MAX decreased by 15% and the off-leakage current increased from 60 nA mm −1 to 10 μ A mm −1 within the temperature range from room temperature to 200 °C.