Evaluation of Internal Structure of GaN High Electron Mobility Transistor

Abstract

Improving the performance of power devices is necessary to perform highly efficient power conversion. Therefore, better power devices made of wide bandgap semiconductors have come to be used. However, most of the complicated structures of GaN-HEMT as high-speed operating devices have not been analyzed in detail. In this study, we clarified the structures of GaN-HEMT by analyzing with the SEM, TEM, EDS, and the multifunctional SPM. We have clarified the existence of fine electrodes and p-type GaN layers near the source and drain electrodes by using SEM. We have clarified the composition of the superlattice strain relief layer of about 5 nm and the AlGaN layer for carrier generation of about 20 nm by using TEM and EDS. We have clarified the dopant polarity of a p-type GaN layer with a thickness of about 300 nm under the gate electrode for normally-off function by using the multifunctional SPM.