*Article* **An Improved 4H-SiC MESFET with a Partially Low Doped Channel**

#### **Hujun Jia \*, Yibo Tong, Tao Li, Shunwei Zhu, Yuan Liang, Xingyu Wang, Tonghui Zeng and Yintang Yang**

School of Microelectronics, Xidian University, Xi'an 710071, China

**\*** Correspondence: hjjia@mail.xidian.edu.cn; Tel.: +86-137-7212-6387

Received: 8 August 2019; Accepted: 21 August 2019; Published: 23 August 2019

**Abstract:** An improved 4H-SiC metal semiconductor field effect transistor (MESFET) based on the double-recessed MESFET (DR-MESFET) for high power added efficiency (PAE) is designed and simulated in this paper and its mechanism is explored by co-simulation of ADS and ISE-TCAD software. This structure has a partially low doped channel (PLDC) under the gate, which increases the PAE of the device by decreasing the absolute value of the threshold voltage (*V*t), gate-source capacitance (*C*gs) and saturation current (*I*d). The simulated results show that with the increase of *H*, the PAE of the device increases and then decreases when the value of *N*PLDC is low enough. The doping concentration and thickness of the PLDC are respectively optimized to be *N*PLDC = 1 × 10<sup>15</sup> cm<sup>−</sup><sup>3</sup> and *H* = 0.15 μm to obtain the best PAE. The maximum PAE obtained from the PLDC-MESFET is 43.67%, while the PAE of the DR-MESFET is 23.43%; the optimized PAE is increased by 86.38%.

**Keywords:** 4H-SiC; MESFET; simulation; PAE
