SiC MESFET
Rajesh C. Panda
EEL 6935
WBG I
Spring 2003
Outline
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Introduction
Literature Review
Theory of MESFET Operation
Advantage of SiC MESFET
SiC Basic MESFET Structure
MESFET Specifications
SiC MESFET Application
Summary
Literature Review
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K. P. Hilton, M. J. Uren, D. G. Hayes, P. J. Wilding, H. K. Johnson, J. J. Guest and B. H. Smith,
"High power microwave SiC MESFET technology", in Workshop on High Performance Electron
Devices for Microwave and Optoelectronic Applications, EDMO, 1999, pp. 71-74.
S.T.Allen, J.W.Palmour, ,C.H.Carter,Jr., C.E.Weitzel, K.J.Nordquist, and L.L.Pond, III, “Silicon
Carbide MESFET’s With 2 W/mm and 50% P.A.E. at 1.8 GHz ” IEEE MTT-S Symposium Digest,
San Francisco, CA, June, 1996, pp. 681-684.
ST Allen, RA Sadler, TS Alcorn, JW Palmour, CH Carter, "Silicon Carbide MESFET‘s for High
Power S-Band Applications”, 1997, IEEE MTT-S Digest, pp. 57-60.
SP Murray and KP Roenker, “An Analytical Model for SiC MESFETs,” Solid State Electr. vol. 46
(10), pp. 195-198, October 2002.
KE Moore, CE Weitzel, Kevin J. Nordquist, Lauren L. Pond, III, John W. Palmour, Scott Allen, and
Calvin H. Charter, Jr., “ 4H-SiC MESFET with 65.7 % power added efficiency at 850 MHz”, IEEE
Electron Device Letters, Vol.18, No.2, February 1997.
Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A Wiley-Interscience
Publication, 1988.
Theory Of MESFET Operation
qΦm
qΦs
qχs
Ec
qΦb
qVbi
EF
ЄF
Metal
n-Type s.c.
Metal
n-Type s.c.
EV
Energy-band Diagram before contact
qΦm = Metal Work Function
qχs = Semiconductor Electron Affinity
Energy-band Diagram after contact
qΦs = Semiconductor Work Function
Reference Energy Level (Vacuum)
Schottky-barrier formed when metal deposited on semiconductor
Ref: Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A WileyInterscience Publication, 1988
Theory Of MESFET Operation
Drain
Source
N+
Gate
n
N+
Depletion Region
Neutral Region
Semi-Insulating Substrate
Ref: http://nina.ecse.rpi.edu/shur/SDM2/Notes/Noteshtm/16MESFET
Theory Of MESFET Operation
S
G
DR
-
D
• VGS controls channel (DR)
• VDS drifts carriers
• Fully depleted channel =
pinch off condition (Vpinch)
Depletion region forms under schottky contact (gate) and controls
the flow of current in the channel (n-type) layer.
Device therefore behaves as voltage controlled switch, capable of
very high speed modulation.
Ref: Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A WileyInterscience Publication, 1988
Theory Of MESFET Operation
Ref: Inder Bahl and Prakash Bhartia, Microwave Solid State Circuit Design, A WileyInterscience Publication, 1988
Theory Of MESFET Operation
VGS=0
VGS = -0.5
Drain
Current
VGS = -1
Drain Voltage
Advantage of SiC MESFET
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Wide Energy Band Gap Device
High Breakdown Electric Device
High Electrical and Thermal Conductivity
High Saturated Electron Velocity
High Melting Point
Chemically Inert
Ref: http://www.sec.gov/Archives/edgar/data/895419/0000895419-99-000009.txt
Advantage of SiC MESFET
Ref: http://www.nt.chalmers.se/mve/wbg.htm
SiC Basic MESFET Structure
Gate
Source (Schottky)
N+ Epi
Active Layer
Drain
N+ Epi
Contact Layer
N-Channel
P-Buffer
High Resistive
Substrate
N-type Substrate
Ref: http://nina.ecse.rpi.edu/shur/advanced/Notes/Noteshtm/Wide19/sld013.htm
Ref: S.P. Murray and K.P. Roenkar, “An Analytical Model For SiC MESFETs”.
MESFET Specifications
Cree 1
Motorola 2
Sony 3
CRF-20010
MRF9811T1
SGM2014AN
SiC MESFET GaAs MESFET GaAs MESFET
Symbol
Units
Pout
G
ηD
dBm
dB
%
38
12
37.5
21
14
55
18
VDSS
VGS
fmax
Vdc
Vdc
GHz
80
-10
20-25
10
-5
2
12
-5
2
W
C
55
0.77
0.1
250
150
125
V(BR)GDO
IDSS
Vdc
Adc
120
1.8
15
0.35
0.028
VGS(th)
gfs
Vdc
S
-12
0.15
-2
0.9
0.017
General Rating
Output Power
Power Gain
Drain Efficiency
Maximum Ratings
Drain-Source Voltage
Gate-Source Voltage
Maximum Frequency
Total Device Dissipation @ 50 o C
Operating Junction Temperature
PD
TJ
o
Off-Characteristics
Gate-Drain Breakdown Voltage
Drain Saturation Current
On-Characteristics
Gate Threshold Voltage
Forward Transconductance
Ref: 1- http://www.cree.com/products/microwave/AppNote_20010_28V-1.0.pdf
2- http://www.mot-sps.com/books/dl110/pdf/mrf9811t1rev0d1.pdf
3- http://www.sel.sony.com/semi/PDF/SGM2014AN.pdf
MESFET Specifications
Comparison of SiC and GaAs MESFET Specifications:
• Drain Source Voltage and Drain Saturation Current
– SiC devices have a higher VDSS and a higher IDSS than
GaAs devices thereby increasing the power handling
capabilities of SiC MESFETs
• Maximum Frequency
– SiC fmax is approximately ten times greater than that found
in GaAs devices
• Device Power Dissipation
– SiC MESFET thermal dissipation greatly exceeds that of
GaAs which allows for greater power handling and higher
temperature operation
SiC MESFET Application
The Major Applications Include :
• Wireless Communication
• Microwave Circuits
• High Power
• High Frequency
• Power Amplifiers
Ref: http://www.cree.com
Summary
The Superior Properties of SiC
MESFET like higher breakdown
voltage, higher thermal conductivity
and higher saturated electron velocity
makes it one of the most promising
devices for high frequency and high
power.