ABSTRACT
Silicon carbide (SiC) metal semiconductor field effect transistor (MESFET) has been a competitive candidate for high power and high frequency applications due to its superior material property, such as wide band gap, high breakdown field, high electron saturation velocity, and large thermal conductivity (Hoon et al. 2006, Zhang et al. 2007, Hossein 2010, 2011, Noorbakhsh et al. 2012, Aminbeidokhti & Orouji 2013). These outstanding characteristics allow 4H-SiC MESEFT to provide significantly higher output power density than the conventional semiconductor materials based devices, which means to obtain the same output power density, 4H-SiC MESFET requires lighter weight and smaller size.As its power and frequency applications, a large breakdown voltage is required for 4H-SiC MESFET while maintaining a high drain current. However, these requirements are contradictory to each other: A high drain current needs a large product of channel thickness and doping concentration (tC ×N ), while to achieve a large breakdown voltage, the channel doping concentration is required to be not too large. Meanwhile, a thick channel will reduce the ratio of gate length to channel thickness (LG/tC), which will lead to a drain induced bias lowering (DIBL) effect and cause a decrease of device performance as well as circuit performance (Zhua et al. 2006, Hossein & Orouji 2012).
