Technology and characterization of GaN-based heterostructure field effect transistors (HFETs)
type: CreativeWork
description: Heterostructure field effect transistors (HFETs) on the basis of Group III nitrides are increasingly gaining importance for the application as RF power amplifier devices. A common feature of the layer structure of such transistors is a GaN buffer which is usually deposited on non-native substrates, e.g. sapphire, silicon or SiC. A subsequent ternary barrier layer, such as AlGaN or AlInN, allows the realization of a so-called two-dimensional electron gas (2DEG) at the GaN interface. Even without further doping and only due to polarisation induced carriers, an approximately triangular quantum well in the GaN buffer can be generated. This structure is characterized by a high sheet carrier concentration as well as by a high mobility. This fact in combination with the outstanding physical properties of GaN (high band gap and high breakdown field) is the precondition for the devices in the above mentioned field of application. In order to realize such HFETs, a baseline process was developed and established at the ITHE. In one part of this thesis, the development and the physical basis of each process step are described. Furthermore, the interactions between different process parameters and the physical properties of the resulting devices were identified and interpreted. During this process, the mesa isolation was refined, the metal semiconductor contacts were improved, i.e. the ohmic contact resistance as well the gate leackage current were reduced, and the whole process chain was optimized in terms of reproducibility and reliability. Although every single process step is important, the surface passivation plays an especially essential role in the device performance. Without a passivation layer, surface-related dispersion effects cannot be minimized or even eliminated. Therefore, one focus of this thesis was the development of such a passivation process. Based on a comparison between the literature on surface passivation and data obtained in experiments, a layer with good…
abstract: Heterostructure field effect transistors (HFETs) on the basis of Group III nitrides are increasingly gaining importance for the application as RF power amplifier devices. A common feature of the layer structure of such transistors is a GaN buffer which is usually deposited on non-native substrates, e.g. sapphire, silicon or SiC. A subsequent ternary barrier layer, such as AlGaN or AlInN, allows the realization of a so-called two-dimensional electron gas (2DEG) at the GaN interface. Even without further doping and only due to polarisation induced carriers, an approximately triangular quantum well in the GaN buffer can be generated. This structure is characterized by a high sheet carrier concentration as well as by a high mobility. This fact in combination with the outstanding physical properties of GaN (high band gap and high breakdown field) is the precondition for the devices in the above mentioned field of application. In order to realize such HFETs, a baseline process was developed and established at the ITHE. In one part of this thesis, the development and the physical basis of each process step are described. Furthermore, the interactions between different process parameters and the physical properties of the resulting devices were identified and interpreted. During this process, the mesa isolation was refined, the metal semiconductor contacts were improved, i.e. the ohmic contact resistance as well the gate leackage current were reduced, and the whole process chain was optimized in terms of reproducibility and reliability. Although every single process step is important, the surface passivation plays an especially essential role in the device performance. Without a passivation layer, surface-related dispersion effects cannot be minimized or even eliminated. Therefore, one focus of this thesis was the development of such a passivation process. Based on a comparison between the literature on surface passivation and data obtained in experiments, a layer with good…
author: Fieger, Michael
language: eng
keywords: info:eu-repo/classification/ddc/620, Heterostruktur-Bauelement, Nitride, HEMT, Ingenieurwissenschaften, HFET, GaN, AlInN, AlGaN
date published: 2010
date modified: 2026-07-30T19:43:35Z
provider: RWTH Aachen University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Publikationsserver der RWTH Aachen University