Expanded Channel in the SOI MESFET by SiGe Regions to Improve the Current Capability and High-Frequency Features

In this paper, a novel structure for silicon on insulator metal semiconductor field effect transistors (SOI MESFETs) is introduced using the heterogeneous Si/SiGe region. SiGe semiconductor is used to expand the effective width of the drift region inside the buried oxide (BOX) layer. Due to its properties such as high electron mobility, high electron drift velocity, and excellent radio frequency (RF) performance, it significantly increases the current density of drain and other DC and RF parameters. Also, to control the critical electric field, which determines the breakdown voltage of the device, as well as to reduce the parasitic capacitance to improve its frequency characteristics, an additional oxide region between the gate and drain and below a part of the gate region is used. Numerical simulation shows that the drain current density and breakdown voltage of the proposed device compared to the conventional structure has been improved by 120% and 37%, respectively, resulting in a 2 times increase in maximum output power density (Pmax). Also, the RF specifications of the new structure, including current gain (h21), unilateral power gain (U), and maximum available power gain (MAG), have been improved by 130%, 85%, and 65%, respectively. These specifications are proper for a device in high power and RF circuits like D-band applications.