SC3: Beyond the Limits of GaN HEMT Technology – Vertical GaN Transistors and Towards AlN Electronics

Dr. Oliver Hilt, Ferdinand-Braun-Institut Berlin

GaN power switching transistors for blocking voltages up to 900 V became commercially available in the last decade and they excel in particularly low gate charge and a low output capacitance. The associated low switching losses are the key to power converters with increased power density and operating at higher switching frequencies. But drawbacks related to the GaN-on-Si hetero-epitaxy being used and the lateral device concept still keep the devices from reaching their theoretical material limits and introduce additional dispersion-related losses during high-voltage switching operation. Furthermore, the lateral device concept comes to its limits above 1 kV and for currents beyond 100 A.

Re-thinking the nitride-based material stack may overcome the current GaN HEMT performance limitations. An AlN-based lateral HEMT technology shows advantages in terms of current density as well as in terms of dispersion and it has strong potential for the next generation lateral device technology. The lecture will discuss concepts, challenges in device fabrication and present device results.

Extending GaN transistor technologies to voltages > 1 kV favors a shift to vertical device architectures. Different vertical device concepts are currently explored for high-voltage GaN switches. Their pros and cons will be presented together with device results. These are set into relation to competing devices based on SiC and to first Ga2O3 device results.

Dr. Hilt received his Ph.D. in Experimental Physics from the Free University Berlin, Germany in 1995 for his work on the charge transport in liquefied rare gases, performed at the Hahn-Meitner-Institut Berlin. He analyzed charge transport in organic conductors and semiconductors for optoelectronic applications at Technical University Delft and University Leiden, both The Netherlands. In 1999 he joined sglux GmbH, Berlin to develop UV photodiodes and promoted to CEO in 2003. Dr. Hilt joined FBH in 2006 for the development of GaN switching transistors for high voltage power applications. He is currently head of the GaN Power Electronic Devices Lab and his work focuses on integration technologies for compact GaN-based power conversion and on explorative ultra-wide bandgap power switching devices.