Mohammad Jozi

Bio: Mohammad Jozi is an academic researcher from Semnan University. The author has contributed to research in topics: Breakdown voltage & Voltage. The author has an hindex of 3, co-authored 3 publications receiving 16 citations.

Control of electric field in 4H-SiC UMOSFET: Physical investigation

Abstract: In this paper, we show how breakdown voltage (VBR) and the specific on-resistance (Ron) can be improved simply by controlling of the electric field in a power 4H-SiC UMOSFET. The key idea in this work is increasing the uniformity of the electric field profile by inserting a region with a graded doping density (GD region) in the drift region. The doping density of inserted region is decreased gradually from top to bottom, called Graded Doping Region UMOSFET (GDR-UMOSFET). The GD region results in a more uniform electric field profile in comparison with a conventional UMOSFET (C-UMOSFET) and a UMOSFET with an accumulation layer (AL-UMOSFET). This in turn improves breakdown voltage. Using two-dimensional two-carrier simulation, we demonstrate that the GDR-UMOSFET shows higher breakdown voltage and lower specific on-resistance. Our results show the maximum breakdown voltage of 1340 V is obtained for the GDR-UMOSFET with 10 µm drift region length, while at the same drift region length and approximated doping density, the maximum breakdown voltages of the C-UMOSFET and the AL-UMOSFET structures are 534 V and 703 V, respectively.

A novel double-gate SOI MOSFET to improve the floating body effect by dual SiGe trench

Abstract: In short-channel silicon-on-insulator metal-oxide-semiconductor transistors (SOI MOSFETs) the high electric field near the drain increases the floating-body effect. The aim of this article is to introduce a novel structure that reduces the electric field near the drain, so improving the floating-body effect. In the proposed structure, a dual trench is created in the buried oxide exactly under the junctions of drain/source and channel and is filled with an n-type SiGe material. The dual trench regions absorb the electric field lines and hence, the electric characteristic significantly improve. The proposed structure is named as dual SiGe trench double gate SOI MOSFET. In addition, we observe a considerable improvement in self-heating effects due to the higher thermal conductivity of SiGe in comparison with silicon dioxide.

Simulation Study of 4H-SiC UMOSFET Structure With p + -polySi/SiC Shielded Region

Abstract: In this paper, we propose an enhanced efficiency 4H-SiC U-shaped trench-gate MOSFET (UMOSFET) structure. The proposed device structure takes an advantage of a p+-polySi/SiC shielded region to reduce the on-state specific resistance. We show that the heterojunction diode formed by the p+-polySi and the n-drift regions improves the body diode effect, and thereby, reduces the reverse recovery charge. Further, we illustrate through simulation results that in comparison with the traditional p+-SiC shielded UMOSFET, the proposed device structure provides a 56.5% improvement in the figure of merit (including the breakdown voltage and on-resistance), and a 35.7% and 55.5% reduction in specific on-resistance and reverse recovery charge, respectively.

The Vanadium Effect on Electronic and Optical Response of MoS 2 Graphene-Like: Using DFT

Abstract: First-principle calculations based on the density functional theory (DFT) with the GGA approximation are done to study the electronic and optical properties of MoS2 and MoS2:V graphene-like(GL) cases. In the pure case, the MoS2 GL has the direct energy gap value of 1.7eV. By absorbing the Vanadium (V) impurity to MoS2 GL structure, its electronic property is changed to Half-metallic behavior, and also the energy gap of MoS2:V GL is reduced to 1.6eV amount in up spin. The MoS2 GL absorption is started in the visible area while a small absorption is occurred in the infrared region at x-direction by adding V impurity, and the real and imaginary parts of the dielectric functions claim to have metallic treatment in the mentioned direction.

β-Ga2O3 Junctionless FET with an Ω Shape 4H-SiC Region in Accumulation Mode

Abstract: In this paper, we present a solution for understanding volume depletion and essentially decreasing the leakage current of β-Ga2O3 junctionless FETs (βJL-FETs) by embedding the 4H-SiC layer into the BOX layer (βESJL-FET). Using the silvaco simulator with 2-D simulations, we illustrate that the βESJL-FET with an embedded 4H-SiC layer shows a very high ION/IOFF ratio of ~1012 even for a 40 nm channel length. The main idea of this work focuses on changing the volume depletion for achieving a lower leakage current. Also, the other goal is obtaining the lower self-heating effect provided by replacing 4H-SiC with a higher thermal conductivity into the BOX layer. Although the silicon FETs are more applicable but, due to better performance at the ultra-scaled dimensions, we propose the β-Ga2O3 instead of silicon. Ga2O3 has a higher effective mass and lower bond distance than silicon and is suitable for short-channel devices.

4H-SiC UMOSFET With an Electric Field Modulation Region Below P-Body

Abstract: In this article, we investigate a novel optimized 4H-SiC U-shaped trench-gate MOSFET (UMOSFET) structure, which features an electric field modulation region below the P-body. This region consists of a p-type region and an n-type region, while the p-type region is wrapped by the n-type region. We use the p-type region to reduce the electric field at the P+ shielding layer and the gate oxide. The reduced electric field increases the breakdown voltage (BV) of the optimized UMOSFET substantially. The n-type region can also improve the ON-state characteristics of the UMOSFET. Under the combined action of the p-type region and the n-type region, the BV and figure of merit increased by 25.2% and 120.5%, respectively. Moreover, the specific ON-resistance dropped by 40.8%.