Development and characterization of GaN high electron mobility transistors for low noise applications.
Date of Issue2011
School of Electrical and Electronic Engineering
This thesis presents the fabrication, detailed characterization and analysis of AlGaN/GaN high electron mobility transistors (HEMTs) and metal-insulator-semiconductor HEMTs (MISHEMTs) for microwave low-noise applications. The major contributions of this thesis are given below: (1) Fabrication processes for conventional Schottky-gate GaN HEMTs and MISHEMTs were developed particularly for low-noise applications. (2) The physical mechanisms of the OFF-state breakdown characteristics were comprehensively studied for GaN HEMTs on Si. (3) The surface passivation effects on the bias-dependent microwave small signal characteristics and noise characteristics have been comprehensively studied for AlGaN/GaN HEMTs on Si. The effects of SiN surface passivation on the bias-dependent small signal equivalent circuit elements have been investigated in detail. (4) The temperature dependent noise performance was characterized for GaN HEMT on high-resistivity Si substrate over a wide temperature range from -50 oC to 200 oC. An analytical model for the temperature dependent microwave noise parameters has been proposed for the GaN HEMTs. (5) A 0.25-um Atomic-Layer-Deposited (ALD) Al2O3/AlGaN/GaN MISHEMT on high-resistivity Si with excellent noise performance was demonstrated. A state-of-the-art minimum noise figure (NFmin) value of 1.0 dB at 10 GHz was achieved for a 0.25 um ALD Al2O3/AlGaN/GaN MISHEMT on Si for the first time. The 2-dimensional-electron-gas (2DEG) density and transport properties in the ALD-Al2O3/AlGaN/GaN MISHEMTs have been studied.
DRNTU::Engineering::Electrical and electronic engineering::Microelectronics