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We propose herein a new dual-gate metal---oxide---semiconductor field-effect transistor (MOSFET) with just a unipolar junction (UJ-DG MOSFET) on the source side. The UJ-DG MOSFET structure is constructed from an $${N}^{+}$$N+ region on the source side with the rest consisting of a $${P}^{-}$$P- region over the gate and drain, forming an auxiliary gate over the drain region with appropriate length and work function (named A-gate), converting the drain to an $${N}^{+}$$N+ region. The new structure behaves as a MOSFET, exhibiting better efficiency than the conventional double-gate MOSFET (C-DG MOSFET) thanks to the modified electric field. The amended electric field offers advantages including improved electrical characteristics, reliability, leakage current, $${I}_{\mathrm{ON}}/I_{\mathrm{OFF}}$$ION/IOFF ratio, gate-induced drain leakage, and electron temperature. Two-dimensional analytical models of the surface potential and electric field over the channel and drain are applied to investigate the drain current in the UJ-DG MOSFET. To confirm their accuracy, the MOSFET characteristics obtained using the 2D Atlas simulator for the UJ-DG and C-DG are analyzed and compared.

We describe herein a 4H-SiC metal---semiconductor field-effect transistor (MESFET) with a novel dual well in the buffer layer. The key idea is to change the channel thickness to decrease the hole concentration and modify the depletion region shape and drain current path in the channel. In the proposed structure, a dual well is created in the buffer layer exactly under the gate. We call this structure the dual-well MESFET (DW-MESFET). The drain current of the proposed structure increases by 34.7 % compared with the conventional structure (C-MESFET) due to the change in channel thickness and modification of the depletion region and drain current path. Also, the maximum power density ($$P_{\mathrm{max}}$$Pmax) and the direct-current (DC) transconductance ($$g_{\mathrm{m}}$$gm) of the DW-MESFET increase by 45.23 and 72.5 %, respectively, in comparison with the C-MESFET structure. Hence, the proposed structure can be used for high-current and high-power applications.

In this paper, a novel symmetrical structure (SS) of 4H---SiC metal semiconductor field effect transistor (MESFET) as an effective way to improve the breakdown voltage is presented. The key idea in this work is to improve the breakdown voltage, maximum output power density, and frequency parameters of the device using a symmetrical structure with recessed gate. The SS-MESFET modifies the electric field in the drift layer significantly. The influence of the SS-MESFET on the saturation current, breakdown voltage $$(\hbox {V}_{\mathrm{BR}})$$(VBR), and small-signal characteristics of the SS-MESFET are studied by numerical device simulation. Using two-dimensional device simulation, we demonstrate that the breakdown voltage $$(\hbox {V}_{\mathrm{BR}})$$(VBR) improved by factors 2.5 and 3.3 in comparison with an asymmetrical conventional MESFET structure (AC-MESFET) and a symmetrical conventional MESFET structure (SC-MESFET), respectively. Also, the maximum output power density $$(\hbox {P}_{\mathrm{max}})$$(Pmax) improved about by 93 and 250 % in comparison with the AC-MESFET and SC-MESFET structures, respectively. So, the SS-MESFET shows the superior maximum available gain (MAG), unilateral power gain (U), and current gain $$(\hbox {h}_{12})$$(h12) which is presenting the proposed structure is more suitable device for high power microwave applications.