Power Semiconductor Devices for Low-Temperature Environments - II Space Power Workshop April 2005, Manhattan Beach, California

2 R. R. Ward, W. J. Dawson, L. Zhu, R. K. Kirschman GPD Optoelectronics Corp., Salem, New Hampshire G. Niu, R. M. Nelms Auburn University, Dept. Electrical & Computer Engineering, Auburn, Alabama O. Mueller, M. J. Hennessy, E. K. Mueller MTECH Laboratories, Ballston Lake, New York R. L. Patterson, J. E. Dickman NASA Glenn Research Center, Cleveland, Ohio A. Hammoud QSS Group Inc., Cleveland, Ohio Supported by NASA Glenn Research Center and ONR/DARPA

3 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

4 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

5 Temperatures for Spacecraft

6 Solar System Temperatures

7 Benefits of Using Low-Temp Electronics Reduce mass & volume Reduce power requirements Reduce spacecraft complexity Reduce disruption of environment Increase operating/mission time Increase overall reliability

8 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

9 Why SiGe? Incorporate desirable characteristics of Si and Ge Can optimize devices for cryogenic applications by selective use of Ge, Si and SiGe SiGe provides additional flexibility through band-gap engineering (% of Ge) Devices can operate at all cryogenic temperatures (as low as ~ 1 K if required) All device types work at cryogenic temperatures –Diodes –Field-effect transistors –Bipolar transistors Compatible with standard semiconductor processing

10 Semiconductor Materials Comparison

11 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

12 Development Program Develop semiconductor devices: diodes, HBTs, MOSFETs, IGBTs Specifically designed for low temperatures For use down to ~ 30 K (~ –240°C) For spacecraft Power Management and Actuator Control

13 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

14 ~0.5 μm n+ Si ~0.4 μm p SiGe ~20 μm n– Si Emitter contact ~150 μm n+ Si Collector contact Base contact Cryo Power HBT Design Example

15 SiGe HBT at +20°C (2004) 20 V 0.2 A ΔI B = 1 mA/step

16 SiGe HBT at –196°C (77 K) (2004) 50 V ΔI B = 0.5 mA/step 0.2 A

17 Cryo Power HBT Epi Wafers Second Generation

18 Cryo Power HBT Die (one design) ~ 4 mm

19 Cryo Power HBT Characteristics 20 V RT 2 A 20 V 1 A LN  I B = 5 mA Gain ~ 75  I B = 0.5 mA Gain ~ 500

20 Cryo Power HBT Characteristics

21 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

22 SiGe Boost Converter Circuit Output capacitor SiGe diode Switching pulse Inductor Load SiGe HBT + – Input capacitor 24 V in48 V out ~20 – 300 K Drive circuit Power supply + –

23 SiGe 100 W Cryo Boost Converter 100 kHz, 24 V in, 48 V out

24 SiGe 100 W Cryo Boost Converter Backside

25 Cryostat for Measuring  100 W Circuits (variable temperature 300 to ~20 K) Vendor’s LHe dewar LHe ~4” Cu cold plate with internal channels Stainless steel tubes GHe vent (not visible) Electrical feedthru ~8” Circuitry Cu circuit plate

26 Cryostat for Measuring  100 W Circuits

W SiGe Power Converter in Cryostat

28 SiGe 100 W Cryo Boost Converter Performance

29 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

30 Summary Cryogenic power conversion is of interest for a range of applications within NASA and elsewhere. For cryogenic power conversion, SiGe devices are potentially superior to devices based on Si or Ge. We are developing SiGe semiconductor devices for cryogenic power applications. We have designed, fabricated, and used SiGe HBTs in power converters operating at cryogenic temperatures and converting >100 W. We will continue development with SiGe MOSFETs and IGBTs.

31 Outline Why low-temperature electronics for space? Why SiGe? Development program Designs and results SiGe heterojunction bipolar transistors (HBTs) Low-temperature power converter Summary Future

32 Future Continue to develop low-temperature power devices –SiGe diodes, SiGe bipolar transistors, –SiGe MOS field-effect transistors –SiGe IGBTs Proposed development of low-temperature power SiGe thyristors (SCRs) Circuit development –Higher-frequency, higher power converters –Motor controllers