Sub-micron p-Channel GaN Tri-gate MISFET

Remarkable attributes of GaN has led to the development of transistor technology for both power electronics and RF applications. Even though much attention is given to n-channel GaN transistor technology, p-channel GaN transistors still lack attention. Development of p-channel GaN transistors is a must to harness the full potential that GaN technology has to offer in achieving high-efficiency power conversion.

In this work, we have demonstrated for the first time sub-micron p-channel tri-gate MISFET with fin width of 200 nm. We show the schematic of fabricated device structure along with device dimensions. We also show the SEM image of the final device and the fins respectively. Because of the relatively thin AlGaN layer, the measurement results show significant electron contribution to the total drain current. However, if we deduct the current due to 2-DEG at the interface of AlGaN/GaN, we can extract the hole current. The IDS-VDS characteristics of the hole current is shown. To prove that the current is not because of the holes in the top p-GaN layer rather than the 2-DHG present at the GaN/AlGaN interface, we performed a low-temperature measurement. Because of relatively higher activation energy of Mg (~240 meV) in GaN, the p GaN layer is expected to be frozen out at around 77K leaving only the 2-DHG channel for the hole current.