A High Channel Mobility and a Normally‐off Operation of a Vertical GaN MOSFET Using an AlSiO/AlN Gate Stack Structure on m‐plane Trench Sidewall

Abstract

We previously developed an AlSiO/AlN‐interlayer gate stack formed on c‐plane GaN metal‐oxide‐semiconductor (MOS) devices to enhance the interface of the gate insulator. By utilizing this gate stack structure, we obtained a channel mobility of over 200 cm2/Vs on c‐plane. However, the threshold voltage was negative because of the polarization charge at the AlN/GaN interface. This study extends the application of this gate stack structure to the nonpolar m‐plane, which is obtained from a trench sidewall. We successfully achieve both a high channel mobility of 150 cm2/Vs and a threshold voltage of 1.3 V, normally‐off operation. This achievement holds significant promise for the gate structure of a GaN trench‐gate MOS field‐effect transistor. The limiting factor of the channel mobility is Coulomb scattering in a low electric field, whereas surface roughness scattering is dominant in a higher field.This article is protected by copyright. All rights reserved.