GaN High Power Electronics

This report details work from the Director's Strategic Initiative (DSI) on Gallium Nitride (GaN) High Power Electronics in which GaN devices are assessed compared to those fabricated from silicon carbide (SiC). For low power applications (1500 V), GaN diodes have a lower on-resistance and less loss than their SiC counterparts because the critical breakdown field and electron mobility are larger. We expect this will also be true for high power electronic (HPE) GaN high electron mobility transistors (HEMTs) compared to SiC metal-oxide semiconductor field-effect transistors (MOSFETs). However, GaN devices are not yet manufacturable because the uniformity of the material across the wafer, and therefore the device properties, vary greatly. While the work at the U.S. Army Research Laboratory (ARL) does not yet match the best work being done in Japan, the reasons for this have been identified as the relatively large carbon background impurity concentration in traditionally grown metal-organic chemical vapor deposition (MOCVD) GaN films and the relatively large resistance of hydride vapor phase epitaxy (HVPE) GaN substrates. Using nontraditional MOCVD growth methods, more heavily doped HVPE GaN substrates, and GaN single crystals that have very recently become available, we expect be able to determine if a process can be developed to manufacture GaN devices that have superior properties to those made from SiC for some important Army applications. The original document contains color images.