Lunedì 9 settembre 2019
Sala Seminari, Piano I, Edificio U5 – via Roberto Cozzi 55, Milano
Relatore: 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.