In situ grown AlN/AlGaN/GaN heterostructure field-effect transistor

In situ grown AlN/AlGaN/GaN metal-insulator-semiconductor (MIS) heterostructure field-effect transistor (HFET) is promising for high power applications due to the reduced gate leakage current together with the successful surface passivation. In this study, we present a novel AlGaN/GaN MIS-HFET using in situ AlN as a gate insulator. The AlN is formed subsequently after the epitaxial growth in the same reactor without any exposure in the air. This “earlier” passivation by in situ AlN protects the surface during processing and neutralizes the charges at the top of AlGaN interface, which leads to a higher electron density of channel and superior device characteristics. The unity gain cutoff frequency (f_T) and maximum frequency of oscillation (f_max) are 14.5 and 24.9 GHz, respectively. The fabricated AlN/AlGaN/GaN MIS-HFET at 2.4 GHz delivers 2.3 W/mm output power density and 21.3% peak power added efficiency. It demonstrates a great potential to the next-generation power transistor.