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Radiation Tolerant Enhancement Mode Gallium Nitride 

eGaN ® FETs in DC-DC Converters 

Johan Strydom 

VP of Applications Engineering 

Efficient Power Conversion 

EPC - The Leader in eGaN ® FETs | March 2013 | GOMAC Tech www.epc-co.com 1

Agenda 

• Background 

• Radiation Tolerance 

• Forward Converter case study 

• Other DC-DC converters 

• Conclusions 


eGaN ® FET Structure 

AlGaN Electron Generating Layer 

Dielectric 

S 

G 

- - - - - - - - - - - - - - - - - - - 

D 

Two Dimensional 

Electron Gas (2DEG) 

GaN 

Aluminum Nitride 

Isolation Layer 

Si 


Parameter Comparison 

Parameter Si MOSFET GaN Comment 

V GS(MAX) ±20 V +6 V/ -5 V 

V SD / body diode 1 V 1.5 V – 2.5 V 

V GS(TH) 2 V – 4 V 0.7 V to 2.5 V Logic- level 

device 

R G ≥1 Ω 0.5 Ω- 0.8 Ω 

R DS(ON) change over 

temp 

V GS(TH) 

change over temp. 

Q RR (rev. recovery 

charge) 

+70 % +60 % 25ºC to 125ºC 

-33 % -3 % ~ No temp. 

dependence 

High 0 Schottky / SiC 

performance 

For 100V devices 


Device Figure of Merit 

• Devices of different sizes / technologies can be 

compared using a Figure of Merit. 

• For given technology, R DS(ON) x Q = ~ Constant 

• Some typical FoMs: 

• Synchronous rectifier (SR) performance α R DS(ON) x Q G 

• Switching performance α R DS(ON) x Q GD 


Device Figures of Merit 

~20x - 40x Improvement 

SR FoM 

Switching FoM 

IRF Rad Hard (R DS(ON) ⋅Q G ) IRF Rad Hard (R DS(ON) ⋅Q GD ) 

eGaN FET (R DS(ON) ⋅Q G ) eGaN FET (R DS(ON) ⋅Q GD ) 


Silicon vs. GaN Comparison 

100 V Commercial 

MOSFETS 

100 V Rad Hard 

MOSFETs 

Lower is better 

100 V eGaN FETs 


Radiation Testing Results 


SEE Radiation Performance 

Voltage 

250 

200 

150 

100 

SEE Heavy Ion Testing - Au 

Fail 

Out of Spec 

Undamaged 

87.2 MeV LET with 

up to 190 V bias 

50 

0 

200 V Gen 1 FETs 200 V Gen 2 FETs 

MIL-STD-750E, METHOD 1080 


Total Dose Results – 100 V 

EPC1001 Gate and Drain-Source Leakage Current 

Leakage Current (micro Amperes) 

1000 

100 

10 

1 

0.E+00 5.E+05 1.E+06 

Radiation Dose 

Data up to 1 MRad 

MIL-STD-750E, METHOD 1019 

Threshold Voltage (V) 

IGSS after VGS 

IDSS after VGS 

IGSS after VGS 

IDSS after VGS 

IGSS after VDS 

IDSS after VDS 

IGSS after VDS 

IDSS after VDS 

2.500 

2.300 

2.100 

1.900 

1.700 

1.500 

1.300 

1.100 

.900 

.700 

EPC1001 Threshold Voltage 

VTH after VGS 

VTH after VGS 

VTH after VDS 

VTH after VDS 

0.E+00 5.E+05 1.E+06 

Radiation Dose 

EPC - The Leader in eGaN ® FETs | March 2013 20112 | | GOMAC Tech 

www.epc-co.com 

10

RH Packaging 


Package/ Drive Considerations 

Gate 

Return 

Kelvin Source 

contact 

V dd 

Gate 

Drain 

V gate 

Load 

I g(on) 

Drain 

Source 

Gate 

In 

Q sw 

I d 

Gate 

Return 

Source 

C bypass 

I g(off) 

(bottom view) 

Driver 

Power Source contact 

• 4 - Pad package separate drive loop from power loop. 

• Separate Kelvin gate return minimizes common source 

inductance. 


1 st Gen RH GaN Product line 

PART NO. VOLTAGE CURRENT PEAK R DS(ON) (mΩ) Q G (nC) 

FOM 

Q G * R DS(ON) 

MGN2915U4A 40 V 33 A 150 A 4 11.6 46.4 

MGN2914U4A 40 V 10 A 40 A 16 3 48 

MGN2905U4A 60 V 25 A 100 A 7 10 70 

MGN2909U4A 60 V 6 A 25 A 30 2.4 72 

MGN2901U4A 100 V 25 A 100 A 7 10.5 73.5 

MGN2907U4A 100 V 6 A 25 A 30 2.7 81 

MGN2911U4A 150 V 12 A 40 A 25 6.7 167.5 

MGN2913U4A 150 V 3 A 12 A 100 1.7 170 

MGN2910U4A 200 V 12 A 40 A 25 7.5 187.5 

MGN2912U4A 200 V 3 A 12 A 100 1.9 190 

(Preliminary) 

U4A 

U4A 


Forward Converter 


Forward Converter Case-Study 

50 W / 225 kHz 

Outputs in series allow 

up to 2 A / 40 W output 

RH 200 V, 60 mΩ MOSFET 

Replace with 

RH 200 V, 25 mΩ eGaN FET 


Device Comparison 

GaN 

Silicon 

Si MOSFET 

RH eGaN FET 


Experimental Setup 

Drain Connection 

Source 

Connection 

Gate Connection 


Efficiency Results 

2.5 % – 5 % improvement in Efficiency 


Estimated Device Losses 

60 % Loss Reduction 


Device Loss Comparison 

Improvement in BOTH conduction and switching losses 


Other DC-DC converters 


Synchronous Buck POL 

Replacing Silicon with GaN 

MGN2915U4A 

• eGaN FET allows increased switching frequency 

• Reduced size / weight of passive components 


GaN vs. Silicon 

Nearly a 10:1 improvement in power dissipated 

Power Loss (W) 

14 

12 

10 

8 

6 

4 

2 

GaN- MGN2015 

IRHMS57Z60 

0 

100 200 300 400 500 600 700 800 900 1000 

Frequency (kHz) 

• Irms= 2A, Vcc= 24Vdc, Duty= 50%, Rds(on)= .0045 ohms 

• Power MOSFET losses can be prohibitive @ 500KHz 

• eGaN FET power loss @ 500kHz < Power MOSFET @ 100kHz! 


Low voltage POL 

12 V IN 

3.3 V OUT 

10 A OUT 

100kHz 

• Highest loss: MOSFETs and Inductor 


POL Efficiency Comparison 

95% 

eGaN FETs = 92.5%, 500kHz 

90% 

12 V IN 

Efficiency 

85% 

80% 

75% 

70% 

65% 

60% 

55% 

50% 

45% 

Rad Hard MOSFETs = 84%, 100kHz 

0 2 4 6 8 10 12 

Output Current 

eGaN 1.5 V 

eGaN 2.5 V 

eGaN 3.3 V 

IR 1.8 V 

IR 2.5 V 

IR 3.3 V 


Conclusions 

• eGaN FETs have exceptional Heavy Ion hardness and 

TID capability beyond 1MRad 

• RH eGaN FETs offer at least 3x improvement in device 

losses. 

• This improvement allows increased switching frequency 

and efficiency while reducing overall size and weight. 

• eGaN FETs allow RH DC-DC to be on par with current 

commercial power supplies. 


The end of the 

road for silicon….. 

is the beginning of 

the eGaN FET 

journey!

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