AlGaN/GaN Heterostructure Field Effect Transistor with Novel High Breakdown Voltage

Abstract

Novel high breakdown voltage AlGaN/GaN HFETs have been developed by using a selective thermal oxidation process for the device isolation of AlGaN/GaN hetero-structure and by using silicon nitride as a dielectric film. The leakage current of thermal oxidation isolation process between two active islands separated by 6 micron drastically reduced 5 order of magnitude smaller than that of conventional mesa isolation. The breakdown voltage between islands of over 400V was obtained. The reverse leak current of gate to drain with SiN film deposited by plasma CVD method exhibited drastic reduction of 3 order of magnitude smaller as compare with SiO₂ film. The fabricated 1.3μm-gatelength HFET showed maximum drain current of more than 500mA/mm, maximum transconductance (gmmax) of 130mS/mm and excellent pinch off characteristics at relatively high drain voltage of over 120V. These results indicate that AlGaN/GaN HFETs by using of thermal oxidation process and with SiN dielectric film are quite suitable for high frequency and high power applications.