Center for Ultra-wide Bandgap Extreme-RF Electronics
Ramon R Collazo
Douglas Lee Irving
Project runs from 09/30/2022 to 09/29/2027
Evolutionary development of a new generation of extreme RF (x-RF) electronics at frequencies>100 GHz and high power based on standard approaches would require a Johnson’s figure of merit (JFOM) orders of magnitude superior to that of wide bandgap materials, such as GaN. The two main material properties that the JFOM considers are critical breakdown field (E c ) and drift saturation velocity. Novel ultra-wide bandgap (UWBG) materials with high critical breakdown fields satisfy the first part of the equation. The saturation velocity limit, however, which determines the transit times and frequency limits, cannot be easily overcome due to significant carrier energy losses from various scattering events. To overcome current limitations, the proposed Ultra-wide bandgap extreme-RF electronics (CUXRFE) is built upon two governing hypotheses: (1) high fields in UWBG materials allow for transport conditions beyond classical, steady state transport and enable ballistic transport or velocity overshoot of electrons, resulting in short transit times unattainable by scaling alone, and (2) in order to exploit intrinsic transient transport phenomena, extrinsic barriers to device performance, such as contacts, surfaces, and interfaces must be addressed.
In order to pursue these governing hypotheses, a mature materials system, free of uncontrolled parasitic effects related to structural imperfections and point defects, is needed. We identify AlN and Al-rich AlGaN, built upon virtually perfect AlN substrates, as an ideal testbed to devise and study the new, high-field (up to 15 MVcm -1 ) transport phenomena in the absence of competing deleterious effects. Our early results confirm that more than one order of magnitude shorter transit times, as necessary for x-RF operation, can be accessed via the new transport phenomena and justify the proposed developmental study.