Al-Ta2O5-GaN Semiconductor Device Structure
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Date
2014-08
Authors
Yeoh, Lai Seng
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
GaN-based semiconductor devices have been extensively investigated for used in high
power and high temperature device applications in order to replace Si which is no longer capable
to fulfill these ever-increasing demands. The characteristics of low leakage current, low oxide
charge density, and high oxide capacitance would be necessary for device-quality GaN-based
MOS devices. Along this, there is a great interest in development of GaN-based MOS transistors.
The foremost work in early 2000s used a thermally oxidized GaN film as the gate dielectric in
MOS structure. In late 2000s, GaN-based MOS with other dielectrics such as Al2O3, MgO,
Sc2O3, Si3N4, SiO2, and Ta2O5 were developed.
In the present work, commercial GaN-on-sapphire wafer was used as the semiconductor.
The gate insulator was obtained by depositing selected oxide materials of SiO2, Al2O3, and Ta2O5
onto GaN using RF-sputtering technique. The gate metal was built by evaporating aluminium
onto the insulator. The deposited insulators were characterized using AFM, XRD, XRF, SEM,
and EDX. On the other hand, C-V, I-V, and Dit measurements were carried out to determine the
electrical characteristics of the MOS structures. The fundamental properties of MOS structures
with SiO2, Al2O3, and Ta2O5 gate dielectrics were studied and compared. Then, case studies of
post-deposition annealing, post-metallization annealing, substrate temperature stress, constant
voltage stress, and light radiation stress were investigated on the Al/Ta2O5/GaN MOS structure.
The research results revealed that MOS structure with high-k dielectric of Ta2O5
possessed the best performance in term of lower oxide charge density, lower interface trap
density, higher storage capacitance, higher dynamic conductivity, stability in high temperature
operation, and durability in constant voltage stress. These characteristics were even better than
the ones reported in some existing literatures.
Description
Keywords
GaN-based semiconductor devices structure