Normally-off operation of recess-gated GaN MOSFET on silicon substrate using AlGaN/GaN source/drain with high 2DEG density

AlGaN/GaN-based HFETs are very attractive for RF and power applications due to their superior properties, such as large critical electric field, a high two-dimensional electron gas (2DEG), and a saturation velocity compared to Si-, GaAsand SiC-based devices. State-of-the-art performances of the AlGaN/GaN HFET already showed that f¿ = 160 GHz and fmax =190 GHz, and outpower = 32.2 W/mm, which were achieved mostly on normally-on device [1~2]. In some applications, for example a power switching, normally-off operation is very important to simplify the design of driving circuits and to reduce power loss during switching. However, it is very difficult to realize normally-off operation from AlGaN/GaN HFETs due to inherently large polarizaion charge at AlGaN/GaN hetero-interface. Many efforts have been given to achieve a successful normally-off operation by fabricating a schottky gate type or a MOS gate type technology.