**1. Introduction**

With the development of the semiconductor industry, SiC, diamond and GaN, the third-generation semiconductor materials, have become a research hotspot because of their high critical field strength, wide band gap and high carrier saturation rate [1–6]. 4H-SiC is used to manufacture power devices such as MESFETs due to its larger band gap and higher electron mobility compared to those of 3C-SiC and 6H-SiC [7]. Nowadays, the mainstream research direction on 4H-SiC MESFETs is to achieve better output power density by making changes to the device structure [8,9]. However, in order to achieve green development, enabling devices to have higher energy conversion efficiency has become a new central issue of research. In the papers An Improved DRBL AlGaN/GaN HEMT with High Power Added Efficiency [10] and An Improved UU-MESFET with High Power Added Efficiency [11], a higher power added efficiency (PAE) was obtained by balancing the parameters of the devices. The PAE of the improved with an ultrahigh upper gate MESFET (IUU-MESFET) and the double recessed barrier layer (DRBL) AlGaN/GaN HEMT increased 18% and 48%, respectively. In the aforementioned research works, PAE simply replaces the RF output power with the difference between output and input power in the drain efficiency equation. A larger PAE means that a larger output power can be obtained under the same input power. This is crucial for sustainable development.

In this paper, an improved 4H-SiC MESFET with a partially low doped channel (PLDC) is designed and simulated to improve the PAE of the 4H-SiC DR-MESFET [12] using ISE-TCAD and ADS. A partially low doped channel is used to balance the parameters of the device by adjusting the doping concentration and thickness. The key to this structure is to improve the AC/RF characteristics of the device and improve the PAE of the device. This ensures that the device has lower energy consumption at the same output power, which has grea<sup>t</sup> significance for RF power amplifier applications. In the second part of this paper, the basic features and simulation process of the PLDC-MESFET are introduced, as are the models used in the simulation. In the third section, the main impact of the PLDC on the parameters and PAE of the device is introduced and the mechanism is discussed. In the fourth section, we conclude that the PLDC is helpful for the improvement of the PAE of the DR-MESFET.
