An injection-enhanced gate transistor (IEGT) is a voltage-driven device for switching large current. Fabricating
insulated-gate bipolar transistors (IGBTs) with high collector-emitter voltage (VCES) is difficult because of a sharp
increase in on-state voltage in the high current region. To overcome this limitation, IEGTs are fabricated using a
unique emitter structure. Additionally, the outstanding turn-off performance and the wide safe operating area of
IEGTs make it possible to reduce the power consumption, shrink the size and improve the efficiency of equipment.
IEGTs are ideal for industrial motor control applications that support today’s social infrastructure, including indus-
trial drive systems and power converters. Toshiba’s IEGTs are available in press-pack type and module type
packages. You can select IEGTs that best suit the power capacity and load characteristics requirements for your
applications.
Features of IEGTs
Principle of Operation
High collector-emitter voltage and low saturation voltage
Wide safe operating area (SOA) equivalent to that of IGBTs (high di/dt and dv/dt)
Simplified and small gate drive circuitry due to voltage drive
High switching speed
4
Cross-sectional structure of an IGBT and the factors that limit its collector-emitter voltage
Figure A shows the cross-sectional structure of a conventional IGBT and the carrier distribution in the N-base region. The carrier
concentration decreases monotonically across the N-base region from the collector electrode to the emitter electrode. In order to
increase the collector-emitter voltage of an IGBT, a deep N-base region is necessary between the collector and emitter electrodes.
However, a deep N-base region leads to an area with lower carrier concentration. The consequent increase in electrical resistance
results in an increase in voltage drop and thus an increase in on-state voltage.
Characteristics of the IEGT gate structure and the injection enhancement (IE) effect
Figure B shows the cross-sectional structure of and the carrier distribution in an IEGT. The IEGT has an IGBT-like structure with
deeper and wider trench gates than the IGBT. This structure increases the gate-to-emitter resistance, preventing carriers from
passing through the emitter side. Consequently, carrier concentration is enhanced near the emitter electrode in the N-base region.
As this phenomenon has the same effect as carrier injection and accumulation, it is called the injection enhancement (IE) effect.
This trench-gate structure helps reduce an increase in voltage drop even at high collector-emitter voltage rating.
Figure A Cross-Sectional View of and Carrier Distribution in an IGBT
Because carrier concentration near the emitter is low, an increase in the collector-emitter voltage
rating leads to an increase in on-state voltage.
Figure B Cross-Sectional View of and Carrier Distribution in an IEGT
Carrier concentration near the emitter is enhanced near the emitter. Consequently, electron
injection increases, reducing on-state voltage.
Hybrid IEGT / SiC-SBD Modules
Intended Applications of IEGTs
Helps reduce
equipment size
1.7-kV/1200-A Hybrid IEGT/SiC-SBD Module
NEDO: New Energy and Industrial Technology
Development Organization
Power Inverter with Hybrid IEGT/
SiC-SBDs for Rail Traction
(NEDO Demonstration Project in 2009 to 2011)
Approx. 40% reduction in
equipment cubic volume
97% reduction in diode
reverse recovery loss
Significant reduction in reverse
recovery current
Reduction in turn-on loss
FRD: Fast Recovery Diode
Volume Comparison
(Including Cooling and Motor Control Unit)
Comparison of Reverse Recovery Loss
Comparisons of Reverse Recovery
Current and Turn-on Loss
(Example: 3.3-kV/1500-A IEGT)
The requirements for rail traction motor control systems include not only low noise and comfortable ride but also compact size, light
weight and energy efficiency. To meet these requirements, Toshiba has developed a Plastic Case Module IEGT (PMI) that incorporates
silicon carbide Schottky barrier diodes (SiC-SBDs).
Injection Enhanced Gate Transistors
(
IEGTs
)
Rail traction Green energy generation
Power transmission &
distribution (T&D)
Industrial motor control and
inverters
3000
1500
0
0
2
4
With SiC SBD
With Si FRD
Time, t
(1 μs / div.)
Collector Current, IC (A)
Turn-on Loss
Eon (J)
IEGT/
SiC SBD
IEGT
Cubic Volume
Forward Voltage, VF (V)
Reverse Recovery Loss, Edsw (J)
0
1 3 5
1
2
–97%
–40%
With SiC SBD
With Si FRD
Deep and Wide
Trench Gates
Carrier
distribution
in the N-base
Electron Current
IE Effect
Hole Current
Carrier
distribution
in the N-base
Electron Current
Hole Current
Increase in
resistance
Emitter Gate
Emitter Gate
P-base
N-base N-base
P-collector
P-base
P-collector
Collector Collector