A Novel MESFET structure by U-shape buried oxide for improving the DC and RF Characteristics

Abstract

For the first time, a new type of silicon on insulator metal semiconductor field-effect transistor (SOI-MESFET), the U-shape buried oxide (UBO) SOI-MESFET, is proposed and investigated. The proposed structure is similar to that of the conventional SOI-MESFET with the exception that the shape of buried oxide is reformed to the U-shape. The influence of U-shape buried oxide on saturation current (ID), breakdown voltage (VBR), and small-signal characteristics of the UBO-SOI MESFET is studied by numerical device simulation and compared with a conventional SOI MESFET (C-SOI MESFET) characteristics. The simulated results show that the U-shape buried oxide has excellent effect on cut-off frequency (fT), maximum oscillation frequency (fmax), maximum available gain (MAG), and unilateral power gain (U) for the UBO-SOI MESFET structure. Also the U-shape buried oxide leads to the enhancement of VBR and ID of the UBO-SOI MESFET structure. The optimized results showed that VBR of the UBO-SOI MESFET is 77% larger than that of the C-SOI MESFET, which meanwhile maintains almost 90% higher saturation drain current characteristics. The maximum output power densities of 0.05 and 0.014W/mm are obtained for the UBO-SOI and C- SOI MESFET structures, respectively, which means about 3.5 times larger output power for the proposed device.