Modelling of HEMT for high power switching application using polarization engineering technique

A normally-off field effect transistor (FET) is designed engineering polarization in Ga-face GaN-based heterostructures with a GaN caplayer and an AlGaN/p-GaN back barrier. This dissertation focuses on development of enhancement-mode AlGaN/GaN HEMTs for high-voltage switching applications. From the simulation results it is seen that an unintentionally doped GaN cap and p-GaN layer depletes the electrons in the channel and presence of Al_0.2Ga_0.8N back barrier pinches off the channel. A positive gate voltage of 0.4 V is achieved for 80 μm long gate devices. The structure does not require any dry etching process for fabrication which makes more uniform and repeatable threshold voltage control in normally-off AlGaN/GaN heterostructure FETs for power switching application.