Comparative study on AlGaN/GaN HFETs and MIS-HFETs

Abstract

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 Angstrom and 2.5 mum, respectively and Al composition of AlGaN layer was 30 %. In our study, we used Al2O3 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 mum 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 p,m gate length. Pulsed I-V characteristics showed that current collapse is effectively removed by PEALD Al2O3.