09 September 2019

Proposal of N-polar AlGaN/AlN HEMT and Growth of N-polar AlN by MOVPE

PhD Course in Materials Science and Nanotechnology

Monday, 9th September 2019
h. 4.15 p.m.
Seminar Room, 1st Floor, U5 Building – via Roberto Cozzi 55, Milano

Lecturer: Narihito Okada  – Yamaguchi University, Japan

Titolo: Proposal of N-polar AlGaN/AlN HEMT and Growth of N-polar AlN by MOVPE

Abstract. A high electron mobility transistor (HEMT) composed of AlGaN/GaN structure has recently been commercialized as a high frequency power device. However, a novel structure is necessary to dramatically improve the performance of HEMTs and herein we proposed a new device structure, the “N-polar (Al)GaN/AlN HEMT” structure. By simulations, we found that the “N-polar (Al)GaN/AlN HEMT” structure enables higher carrier concentration compared to that of the conventional AlGaN/GaN structure. In addition, N-polar (Al)GaN/AlN HEMT has possibility to achieve high breakdown voltage and high temperature operation owing to the AlN substrate. To realize high performance HEMTs, the flat underlying layer is required. In the case of N-polar (Al)GaN/AlN HEMT, an atomic level flat N-polar AlN is required. We present the effects of N-polar AlN surface morphology on the misorientation angle of a sapphire substrate, which is effective to N-polar GaN. To prepare high quality AlN, we also grew N-polar AlN on a N-polar AlN bulk substrate.