Jun 21, 2016

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

Highlights

4H-SiC UMOSFET is presented to improve the electrical characteristics.
The key idea is increasing the uniformity of the electric field distribution.
A region with a graded doping density is inserted in the drift region.
Breakdown voltage and specific on-resistance of the new structure are improved.

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.

Graphical abstract

We propose a novel power 4H-SiC UMOSFET using control of the electric field in order to improve the breakdown voltage (VBR) and the specific on-resistance (Ron).
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Keywords

  • UMOSFET
  • Electric field
  • 4H-SiC
  • Specific on-resistance
  • Breakdown voltage
    • source:sciencedirect
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