SLIDE 1 Wide Bandgap Semiconductors for Microwave Power Devices
Consultant: Wide Bandgap Power Devices
SLIDE 2 Presentation Outline
- Why Wide Bandgap Semiconductors?
- SiC Microwave Power Devices
- What are FET Field‐Plates?
- AlGaN/GaN Microwave Power Devices
SLIDE 3 The Rest of the Wide Bandgap story
- SiC produced the first commercial BLUE LED’s
- GaN produced first high brightness BLUE LED’s
- GaN based materials enabled and dominate the
LED commercial market
- Low intrinsic carrier concentraKon enables
significantly higher operaKng temperatures
- GaN‐on‐Si looks promising for Switching Power
Devices to compete with silicon IGBT’s, silicon MOSFET’s, and SiC MOSFET’s.
SLIDE 4 Why Wide Bandgap Semiconductors?
- B. Ozpineci and L.M. Tolbert, “Comparison of Wide‐Bandgap Semiconductors for
Power Electronic ApplicaKons,” Oak Ridge NaKonal Laboratory, December 12, 2003 RelaKve Cost $ $$ $$$$$ $$$$$ $$$$ $$$$$$$$$$
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- Wide bandgap enables high breakdown voltages
- This enables a tradeoff between operaKng voltage and
current, but in either case boosts power handling capability
- B. Ozpineci and L.M. Tolbert, “Comparison of Wide‐Bandgap Semiconductors for
Power Electronic ApplicaKons,” Oak Ridge NaKonal Laboratory, December 12, 2003
Diode Breakdown Voltages
SLIDE 6
- Wide bandgap enables lower device resistance for a given voltage
- Lower resistance enables higher operaKng current
- B. Ozpineci and L.M. Tolbert, “Comparison of Wide‐Bandgap Semiconductors for
Power Electronic ApplicaKons,” Oak Ridge NaKonal Laboratory, December 12, 2003
Diode Drift Region Resistance
SLIDE 7 RF Power Density / Operating Voltage
48V
SLIDE 8
Micropipes Result from Screw Dislocation
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Reduction of Micropipe Density / Wafer Size
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Very Low Micropipe Density SiC Wafer
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SiC MESFET --- the first wide bandgap microwave power transistor SiC MESFET’s, SiC MOSFET’s & SiC SIT’s
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Probably Highest SiC MESFET power density ever reported I would certainly like to know more details about this device
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SLIDE 17 High power 4H‐SiC staKc inducKon transistors (SITs)
Measured staKc I‐V characterisKcs of a SIT SEM photo of a SIT device. The mesa fingers are 1 µm wide and 100 µm long. The total mesa length is 1 cm (100 fingers).
SLIDE 18 Microsemi introduced a 2.2kW SiC SIT in Sept. 2010
SLIDE 19
What are Field-Plates? aka - Step-Gates, Faraday Shields, Source connected Field-Plates
Field‐plate is a metal structure added to a FET between the gate and drain that increases the microwave gain and/or breakdown voltage (Si, GaAs, SiC, GaN).
SLIDE 20 Microwave Field-Plates
- First demonstraKon of field‐plate
- n microwave transistor (GaAs)
- Source connected field‐plate sits
- n top of a dielectric
- RF gain is increased by making the
device more unilateral
- CGD is reduced at the expense of CGS
and CDS
- Can also increase breakdown
voltage if properly designed
Source Drain Gate Field Plate Dielectric
SLIDE 21
Field‐Plate increases small signal gain approx. 3 dB
SLIDE 22 1.7 W/mm 1.5 GHz Vds = 35V
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2003
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Field‐Plate increases CW gain 2 dB
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AlGaN–GaN Field Effect Transistor
‐ the SiC MESFET “KILLER”
SLIDE 30 Basic AlGaN‐GaN HeterojuncKon FET
Substrate: Sapphire, SiC, or Silicon
+++++++++++++++++++++
Spontaneous and Piezoelectric PolarizaKon cause +++ charge in the AlGaN. The band structure forms a quantum well at the AlGaN‐GaN interface. Electrons fill the quantum well to a very high density > 1E7 cm‐2. There is no intenKonal doping.
SLIDE 31 Small Signal GaN HFET reported at SiC Conference in Kyoto, Japan
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12.6 mm AlGaN/GaN HFET 48 V 2.14 GHz 74 W 5.9 W/mm No Field Plate IMS 2006
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AlGaN/GaN HFET 30 V 15 GHz 60 W ~ 3 W/mm IMS 2010
SLIDE 41 Wide Bandgap Summary
‐ high operaKng voltages ‐ high thermal conducKvity (SiC substrate)
- SiC MESFET first wide bandgap microwave
power transistor
‐ increased RF gain ‐ even higher operaKng voltages
- AlGaN/GaN heterojuncKon achieves current
density > 1 x 1013 A/cm2 (SiC MESFET “killer”)
- Heavily supported for US defense applicaKons,
but is there a “killer” commercial applicaKon??
