"AlGaN/GaN Current Aperture Vertical Electron Transistors for High Power Electronics"

Srabanti Chowdhury, UCSB ECE Department, Ph.D. Defense

July 28th (Wednesday), 1:00pm
ESB 2001

AlGaN/GaN HEMTs have shown significant performance in both high frequency and high power applications. However, to this date majority of the work has been on the lateral device topologies due to the horizontal nature of the 2D-electron gas (2DEG). For high-power applications, vertical topology devices are preferable over lateral devices to avoid surface arcing which leads to premature device destruction. Vertical geometry is also preferred for ease of packaging and reduction of chip area. An added advantage is the mitigation of surface-state related DC-RF dispersion since high-field regions are buried below the gate electrode. A CAVET is a vertical device with source and gate on top and a current aperture that allows current to flow vertically down from the source to the drain. It has a current blocking layer to block current flowing vertically through any other path but the aperture. CAVETs were demonstrated at UCSB back in 2000 and developed for RF-power application.

Availability and future prospects of good quality bulk GaN substrates inspired a revisit and redesign of CAVETs for high power application. The work unfolded several challenges in growth and processing and each of those led to solution that has more generic impact. Recent results on CAVET have shown low on resistance (less than 2.5mΩ-cm2) and breakdown field of 100V/μm, a value which is 3 times that of the theoretical limit in Si. These results achieved at such early stages of development make the device look very promising for future GaN-based power electronics.

Hosted by: Professor Umesh K. Mishra