Analysis of the subthreshold characteristics in AlGaN/GaN HEMTs with a p-GaN gate

Abstract

In this letter, we analyze the subthreshold characteristics in p-GaN/AlGaN/GaN high electron mobility transistors (HEMTs) with two different Mg flow, i.e., 300 sccm and 750 sccm. The device with 750 sccm Mg flow shows a high threshold voltage and large subthreshold swing (SS). The frequency dependent C-V measurement is reported in p-GaN/AlGaN/GaN heterostructure, showing an obvious frequency dispersion in the device with a high Mg flow. Furthermore, the equivalent circuit network with considering the series of a Schottky metal/p-GaN junction capacitor (CSchottky) and the AlGaN barrier capacitor (CAlGaN) is proposed to calculate the interface state density (Dit) via the conduction method. Finally, a strong correlation between SS, Dit and Mg flow can be concluded, pointing out that the optimization of Mg out-diffusion in p-GaN is crucial to improve the subthreshold characteristics.