通过应力调控提升迁移率的氮极性GaN/AlGaN异质结构

Nitrogen-polar (N-polar) GaN/AlGaN heterostructures hold tremendous promise for the fabrication of high-frequency millimeter-wave high electron mobility transistors (HEMTs). However, the preparation of N-polar GaN/AlGaN heterostructures with high two-dimensional electron gas (2DEG) mobility remains challenging. In this work, we demonstrate that the stress state of the epitaxial heterostructures plays a critical role in modulating the 2DEG mobility. By engineering the stress state of the high-resistance N-polar GaN template from tensile stress to weak compressive stress, we observe a remarkable enhancement in room-temperature 2DEG mobility from 820 to 1420 cm2/V s. Importantly, through theoretical calculations, we elucidate the mechanism by which the stress state affects the 2DEG mobility. Moreover, we further boost the 2DEG mobility to 1730 cm2/V s by introducing a thin AlN interlayer at the GaN/AlGaN interface. This is a high mobility value reported for MOCVD-grown N-polar GaN/AlGaN heterostructures on SiC substrates. This work could promote the development of N-polar GaN/AlGaN based HEMTs with high frequency and high output power.