Experimental Investigations on the Electrical Properties of 4H-SiC Power MOSFETs Under Biaxial and Uniaxial Mechanical Strains

In this letter, we comprehensively investigate the electrical properties of the 1200 V planner-gate 4H-SiC power metal–oxide–semiconductor field-effect transistors under the mechanical strains. Three kinds of strains, including the biaxial strain, uniaxial strain parallel to the gate channel, and uniaxial strain perpendicular to the gate channel, are applied using the wafer bending system. It is found that all kinds of compressive strains improve the drain current (
I_d
) under the same gate voltage (
V_g
) and shift the threshold voltage (
V
_th
) negatively, while the tensile strains decrease
I_d
and shift
V
_th
positively. The
V
_th
shift mainly results from the strain modulated band structure in the poly-Si gate. Under the same overdrive gate voltage (
V
_ov
), biaxial strains merely change
I_d
, while both the parallel and perpendicular uniaxial compressive strains enhance
I_d
. The uniaxial compressive strain elevates the electron mobility in the inverted channel by repopulating more electrons into the valleys with a smaller conduction effective mass, which results in the current improvement.