DISSERTATION REPORT ON POLARIZATION MODELING OF GaN HEMT

Abstract

During the past few decades, immense progress has been made in the development of group III (Ga) – N based devices. GaN-based RF power devices have made substantial progresses due to its potential in high operation voltage, high output power density and high input impedance, which is due to high sheet charge density, high breakdown field and high electron saturation velocity. This work presents an AlGaN/GaN high electron mobility field effect transistor (HEMT) nonlinear model incorporating polarization fields induced by strain at the heterojunction of HEMT. Experimental work done in AlGaN/GaN HEMT has shown that the polarization charges are nonlinear function of the composition of AlGaN/GaN HEMT. Polarization fields induced by strain greatly affect the properties and behavior of AlGaN/GaN HEMT. This work provides AlGaN/GaN HEMT model that includes a nonlinear approximation of the polarization charges at interface of the device. The effect of strain relaxation on the sheet carrier density and threshold voltage for different mole fraction of Aluminum in barrier layer and its thickness is also presented.