Contacts to Gallium Nitride for Power Electronics

Schottky barriers and ohmic contacts to gallium nitride are critical for high-power electronics, which are important to the Navy. Re,searchers at The Pennsylvania State University will investigate metallizations for Schottky diodes to n-type gallium nitride that of,fer potential for reliable high-power operation in vertical diodes fabricated on gallium nitride wafers. The high work functions and, stability of these metallizations could also make them suitable for ohmic contacts to p-type gallium nitride operating at elevated,temperature in high-power vertical PiN diodes. From a fundamental point of view, researchers will investigate metallization processe,s and their impact on electronic properties and device performance. The metallizations will include unreactive stable elements, comp,ounds, and alloys. Metallizations in general can be prepared using evaporation, electron-beam evaporation, sputter deposition, plasm,a atomic layer deposition, and thermal atomic layer deposition. This study will include metallizations for which the effect of the d,eposition method on device performance can be isolated. Penn State researchers will examine the nature of process-induced defects as, well as defects created by high-current stressing. While Penn State will examine stability at high temperatures as a screening mech,anism, they will supply devices to collaborators at the Naval Postgraduate School and United States Naval Academy to perform testing, under high-current stress. Afterwards, devices will be examined to learn about the origins of failure, such as diffusion along disl,ocations in the semiconductor, changes in the population of states in the band gap of gallium nitride, or metallurgical failures, wh,ich could include formation of new interfacial reaction products, loss of adhesion, or unexpected causes. The project also includes,the important goal of training students at Penn State, hosting Midshipmen from the United States Naval Academy, and collaborating wi,th students at the Naval Postgraduate School. Insights gained from this project are expected to be broadly useful to the field of hi,gh-power electronics and to specifically further knowledge on contacts for vertical high-power devices fabricated on gallium nitride, wafers.