Comparative study on AlGaN/GaN HFETs and MIS-HFETs

We report some comparative results on AlGaN/GaN heterostructure field effect transistor (HFET) and metal insulator semiconductor (MIS)-HFET. The AlGaN/GaN HFET and MIS-HFET studied were grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrate. The thickness of undoped AlGaN and GaN were 250 Å and 2.5 μm, respectively and Al composition of AlGaN layer was 30 %. In our study, we used Al ₂O ₃ simultaneously for channel passivation and as a gate insulator which was deposited by plasma enhanced atomic layer deposition (PEALD). The HFETs and MIS-HFETs were fabricated on the same wafer. The HFET showed that the maximum drain current was 550 mA/mm and the maximum transconductance was 200 mS/mm, with a 1.2 μm gate length. The MIS-HFET showed that the maximum drain current was 1300 mA/mm, maximum transconductance was 140 mS/mm, and gate leakage current was 20 pA with a 1.2 μm. gate length. Pulsed I-V characteristics showed that current collapse is effectively removed by PEALD A1 ₂O ₃.