AlN/AlGaN/GaN Metal Insulator Semiconductor Heterostructure Field Effect Transistor

We present the characteristics of a novel AlN/AlGaN/GaN metal insulator semiconductor heterostructure field-effect transistor (MIS-HFET) structure with an AlN cap layer as a gate insulating layer. The gate leakage current for the AlN/AlGaN/GaN MIS-HFET was shown to be more than three orders of magnitude smaller than that for the AlGaN/GaN HFET at around -20 V gate bias. This demonstrates that the wide band gap AlN/AlGaN gate structure suppresses the gate leakage current, resulting in improved device characteristics compared with common HFETs in this study. A maximum gm of 134 mS/mm was observed at a 4 V drain-source bias of a MIS-HFET with a gate length (Lg)=0.85 µm, gate width (Wg)=57 µm, and drain-source spacing (Lds)=3 µm. A threshold voltage (Vt) of -3.06 V and a maximum channel current of 551 mA/mm were observed.