Detailed Study of Breakdown Voltage and Critical Field in Wide Bandgap Semiconductors

A study comparing the breakdown voltage and critical field of various wide bandgap semiconductors (β-Ga
₂
O
₃
, GaN, 4H-SiC) relevant for power electronics, as well as Si, is presented. We used Gauss's law to solve the electric-field profile within p-i-n structures, where the i-layer is doped n
^-
, and we employed field-dependent impact-ionization coefficients from the literature to compute the breakdown voltage of those p-i-n structures as a function of doping and thickness of the blocking i-layer. Instead of treating the critical field as a constant material property, it is shown that the critical field varies not only as a function of doping, but also with device geometry. Furthermore, we have found that even though GaN has a higher critical field, it does not necessarily lead to a larger maximum blocking voltage than that of SiC.