Improvement of DC Characteristics in AlGaN/GaN Heterojunction Field-Effect Transistors Employing AlN Spacer Layer

AlGaN/GaN heterojunction field-effect transistors (HJFETs) employing an AlN spacer layer have been fabricated. By employing the AlN spacer layer, the two-dimensional electron gas (2DEG) mobility increased from 650 cm 2 /(V·s) to 950 cm 2 /(V·s). With regard to DC operating characteristics, the maximum transconductance g mmax increased from 100 mS/mm to 125 mS/mm. In addition, the Schottky barrier at the gate electrode improved, and the saturation current I s decreased from 1.0 × 10 -9 A to 6 × 10 -11 A.