Recently, much attention has been paid to the commercial advent of 600 V rated GaN-on-Si based power devices [1,2].  This is, in part, due to the many obvious advantages of such devices over their silicon and silicon carbide based alternatives. Principally, the large advantage in performance/cost such as $/mΩ of on-resistance of nearly a factor of 10 compared to Si superjunction or SiC FETs. 

 

There has been, however, much less discussion of the significant benefits of GaN-on-Si based power devices at substantially lower voltage ratings, for instance between 80 and 250 V.  One reason for this may be the relatively small and highly segmented market for these medium voltage devices, some $1 billion, compared to the nearly $5 billion market for 600 V rated power devices.  In addition, the advantage of medium voltage GaN based power devices may not be as apparent as at higher voltages, where the higher breakdown field strength of the materials involved in the GaN based HEMTs provide a clear advantage in on-resistance when compared to silicon based alternatives. 

At device ratings of 80 to 250 V, the main performance advantage of GaN based HEMTs over silicon FETs is the nearly 100-fold improvement in minority carrier reverse recovery charge (Qrr).  In fact, there are negligible holes present in the operation of GaN based HEMTs.  While, this is also true for SiC based FETs, the very low channel mobility and expensive cost structure of these devices makes SiC FETs non-viable for wide spread commercial adoption at voltages below 1200 V.