Publication: Design and characterization of ganbased high electron mobility transistor (hemt) devices: improving current collapse and breakdown voltage for modern power devices
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Date
2024-05-01
Authors
Islam Naeemul
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Wide bandgap (WBG) semiconductors such as Gallium Nitride (GaN) and
Silicon Carbide (SiC) are emerging as promising alternatives to Silicon (Si) for new
generations of high efficiency power devices. GaN has attracted a lot of attention
recently because of its superior material properties, leading to the potential realization
of power transistors for high power, high frequency, and high temperature
applications. However, GaN-based high electron mobility transistors (GaN HEMTs)
have some limitations that degrade the device performance, such as current collapse,
higher temperature environment, higher electric field at the gate edge, surface hopping,
impact ionization, and buffer breakdown. The objectives of this research work includes
three areas of GaN HEMT devices. Firstly, temperature impact is investigated on the
Depletion-mode (D-mode) Aluminium Gallium Nitride/Gallium Nitride
(AlGaN/GaN) Metal Oxide High Electron Mobility Transistor (MOSHEMT) device,
where it is observed that higher temperatures degrade the device characteristics curve,
two-dimensional electron gas (2DEG), and 2DEG sheet carrier density. Secondly,
different techniques are applied on D-mode GaN HEMT, Enhancement-mode (Emode)
Metal
Insulator
High
Electron
Mobility
Transistor
(MISHEMT),
and
E-mode
MOSHEMT
devices
to
improve
breakdown
voltage
and
reduce
current
collapse.
Thirdly, a
previous
device
with a
similar
technique
is
implemented
on
the
devices
to
improve
performance
by
reducing
the
electric
field.
Thus,
this
thesis
investigates
these
issues,
presents
approaches
to
address
the
problems,
and
implements
different
methods
using
physics-based
TCAD
simulation,
such
as
Silvaco
TCAD
ATLAS
tools.
The
use
of
numerical
device
simulation
enables
the
validation
of
the
analytical
model
and
facilitates
the
examination
of
the
influence
of
various
device
parameters.
However,
in
the
D-mode
GaN
MOSHEMT
device,
by
varying
the
temperature
to 75
C,
the current collapse was observed. Additionally, the device performance degrades due
to the unmature behaviors of GaN materials when it operates at higher power
dissipation and poor thermal conductivity. On the contrary, the breakdown voltage
achieved above 1000 V; reduced the current collapse by 70 % on the D-mode GaN
HEMT, E-mode GaN MISHEMT, and MOSHEMT devices by implementing different
types of methods like field plate, higher passivation layer, interface charge and carbon
doping, for instance; in E-mode MISHEMT, breakdown voltage reaches to 1370 V.
and reduced current collapse more than 80 %. Moreover, the electric field of the device
achieved less than 5 MV/cm on the same devices by following similar techniques; for
example, in E-mode GaN MOSHEMT, the electric field decreased from 21 MV/cm to
o
o
C and 125
1.5 MV/cm. It is concluded that this result makes our device more reliable for power
device applications.