A comprehensive model of frequency dispersion in 4H–SiC MESFET
Hongliang Lu
*
, Yimen Zhang, Yuming Zhang, Tao Zhang
Microelectronics Institute, Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices of the Ministry of Education, Xidian University, Xi’an 710071, China
article info
Article history:
Received 2 January 2008
Received in revised form 10 December 2008
Accepted 24 December 2008
Available online 5 February 2009
The review of this paper was arranged by
Prof. A. Zaslavsky
PACS:
71.20.b
72.10.d
73.20.+q
Keywords:
4H–SiC
Metal semiconductor field effect transistor
(MESFET)
Trap effect
Frequency dispersion
abstract
A comprehensive model to accurately and simply describe the trapping property and its influence on
device frequency characteristics is proposed for SiC MESFET. DC performance is simulated and trap
parameters are extracted. Both positive and negative frequency dispersions of transconductance are sim-
ulated and analyzed with deep level traps and self-heating effects. Good agreements with reported
results are obtained.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
Silicon Carbide is a promising candidate for high temperature,
high power, high frequency and radiation hardness applications
due to its excellent physical properties such as a wide bandgap,
high critical breakdown electrical field intensity, high thermal con-
ductivity, and high saturation electron drift velocity. With excel-
lent figure of merits compared with other types of SiC, 4H–SiC
metal semiconductor field effect transistor (MESFET) is a potential
candidate for the applications in HDTV systems, phased array ra-
dars and next generation mobile communication base station [1].
However, 4H–SiC MESFET, as same as GaAs MESFET, shows low
frequency dispersion in their transfer and output characteristics,
which may cause significant errors in the estimation of output
power and power conversion efficiency in high-frequency power
amplifier design [2]. These are known to be due to the traps and
self-heating effects [3,4]. Siriex showed that the dispersion is
caused by traps between the buffer layer and the substrate [5].
And Gassoumi explained the mechanism of the effect of surface
state [6]. Sghaier investigated both the vanadium doped substrates
grown by classical physical vapor transport (PVT) and the extre-
mely low vanadium content semi-insulating substrates grown by
high temperature (HTCVD). Trapping effect and frequency disper-
sion had been observed in the case of PVT substrates. In case of
HTCVD very low vanadium substrates, no parasitic effect has been
observed [7]. The origin and mechanism of frequency dispersion in
4H–SiC MESFET are still not clear. Hence, a frequency dispersion
model has been needed for large signal circuit design, which is
accurate and easy to implement and extract model parameters [8].
In this paper, frequency dispersion of the transconductance and
the overall resistance of 4H–SiC MESFETs are analyzed. A compre-
hensive model is used to evaluate the deep-level traps and their
effect on the MESFET devices. The mechanism of the transconduc-
tance and the overall resistance of 4H–SiC MESFETs are discussed
in detail.
2. Physical and analytical model
For 4H–SiC devices, the mobility model is very important for the
DC and AC simulation. At low electric fields, considering acoustic
phonon scattering, polar optical phonon scattering, zero and first
order optical inter-valley phonon scattering, and ionized impurity
0038-1101/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.sse.2008.12.004
* Corresponding author. Tel.: +86 29 88201644; fax: +86 29 88201930.
E-mail address: hllv@mail.xidian.edu.cn (H. Lu).
Solid-State Electronics 53 (2009) 285–291
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Solid-State Electronics
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