Unique opportunity to harness polarization in GaN to override the conventional power electronics figure-of-merits

Owing to the large breakdown electric field (E
b
), wide bandgap semiconductors (WBGs) such as SiC, GaN, Ga
2
O
3
and diamond based power devices are the focus for next generation power switching applications. The unipolar trade-off relationship between the area specific-on resistance (R
on,sp
) and breakdown voltage (BV) is often employed to compare the performance limitation among various materials. The advanced features in benchmarking power devices include conduction modulation and superjunction in devices taking advantage of bipolar conduction. To this end, the GaN material system has a unique advantage due to its prominent spontaneous and piezoelectric polarization effects in GaN, AlN, InN, Al
x
In
y
GaN alloys and flexibility in inserting appropriate heterojunctions thus dramatically broaden the device design space. For instance, Al
x
GaN, which has a larger bandgap, can be designed into the highest field region. Another enabling feature in the GaN material system is polarization doping or Pi-doping: by compositionally grading Al
x
In
y
GaN, both electron and hole doping can be achieved, exhibiting the ideal dopant behavior - no temperature dependence or frequency dependence! This dopant characteristics can't be taken for granted for WBGs based on the knowledge in Si. Pi-doping is an extremely powerful attribute since all wide bandgap semiconductors face the challenge of deep dopants while this ideal solution exists in GaN.