Prediction of high-density and high-mobility two-dimensional electron gas at AlxGa1−xN/4H-SiC interface

This work presents theoretical demonstration of two-dimensional electron gas (2DEG) at the interface between Al
_0.2
Ga
_0.8
N and 4H-SiC, based on the self-consistent solution of Schrödinger-Poisson equations. High sheet carrier density of 1.1×10
¹³
cm
^-2
was obtained in the Al
_0.2
Ga
_0.8
N/4H-SiC heterostructure, which is comparable to the electron concentration in Al
_0.2
Ga
_0.8
N/GaN heterostructure. The current-voltage characteristics of a high-electron-mobility transistor (HEMT), based on the Al
_0.2
Ga
_0.8
N/4H-SiC heterostructure, show a saturated drain current of 1.5 A/mm at the gate voltage of 2 V and the transconductance of 194 mS/mm at -3.95 V. In spite of interface-roughness scattering and phonon scattering, the 2DEG at the Al
_x
Ga
_1-x
N/4H-SiC interface exhibits high electron mobility values of 3365 cm
²
/ (V·s) at 77K and 1120 cm
²
/ (V·s) at 300K. These results indicate that Al
_x
Ga
_1-x
N/4H-SiC heterostructure can significantly improve the mobility of SiC based power switching devices.