SiGe Semiconductor Devices for Cryogenic Power Electronics – III

1. SiGe Semiconductor Devices for Cryogenic Power Electronics – III IMAPS Advanced Technology Workshop on Reliability of Advanced Electronic Packages and Devices in Extreme Cold Environments Pasadena, 21-23 February 2005

2. Outline • The Team and Coordination • Goals & Applications • Technical Objectives & Approach • SiGe Cryo Power HBTs • SiGe Cryo Power Converters • Summary & Plans

3. The Team 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. of Electrical and Computer Engineering, Auburn, Alabama O. Mueller, M. J. Hennessy, E. K. Mueller MTECH Labs./LTE, Ballston Lake, New York R. L. Patterson, J. E. Dickman NASA Glenn Research Center, Cleveland, Ohio A. Hammoud QSS Group Inc., Cleveland, Ohio

4. Coordination NASA SBIR Phase I and II DARPA STTR Phase I

5. Outline • The Team and Coordination • Goals & Applications • Technical Objectives & Approach • SiGe Cryo Power HBTs • SiGe Cryo Power Converters • Summary & Plans

6. Overall Goal • Semiconductor devices (diodes and transistors) • For power management and distribution (PMAD) • Electrical power storage and transmission • Power conversion for motors/generators • For superconducting or cryogenic systems • Temperatures down to ~20 K

7. NASA Interest • Cryogenic systems for spacecraft/aerospace • Cold Solar System sites • Fly-by, orbiting, landers, rovers, penetrators, ... • Propulsion systems • Power generation/storage/distribution systems

8. Solar System Temperatures

9. Temperatures for Spacecraft

10. Specific NASA Technical Goals • Demonstrate SiGe devices at cryogenic temperatures, down to ~20 K • Device types: SiGe HBTs, MOSFETs, IGBTs • Demonstrate SiGe superiority over Si devices for cryogenic power circuits

11. Coordination Separate STTR Program from DARPA Phase I, June - December 2004 with Auburn University

12. NASA in bold, DARPA Phase II in gray Coordination – Goals

13. Outline • The Team and Coordination • Goals & Applications • Technical Approach • SiGe Cryo Power HBTs • SiGe Cryo Power Converters • Summary & Plans

14. 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

15. Materials Comparison

16. P-N Junction (Diode) Forward Voltage

17. SiGe Bandgap 90 K G. Theodorou et al., “Structural, electronic, and optical properties of strained SiGe alloys,” Phys Rev B, vo.l 50, pp. 18355-18359, 15 Dec. 1994.

18. Outline • The Team and Coordination • Goals & Applications • Technical Objectives & Approach • SiGe Cryo Power HBTs • SiGe Cryo Power Converters • Summary & Plans

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

20. A Cryo Power HBT Die ~4 mm

21. Cryo Power HBT Characteristics LN RT 2 A 1 A 20 V 20 V IB = 5 mA Gain ~ 75 IB = 0.5 mA Gain ~ 500

22. Cryo Power HBT Characteristics

23. Outline • The Team and Coordination • Goals & Applications • Technical Objectives & Approach • SiGe Cryo Power HBTs • SiGe Cryo Power Converters • Summary and Plans

24. + Power supply – SiGe Boost Converter Circuit 24 V in 48 V out Inductor SiGe diode + Input capacitor Output capacitor Load SiGe HBT – Drive circuit ~10 – 300 K Switching pulse

25. SiGe 100 W Cryo Boost Converter100 kHz, 24 V in, 48 V out

26. SiGe 100 W Cryo Boost ConverterBackside

27. Cryostat for Measuring 100 W Circuits(variable temperature 300 to ~20 K) ~ 4” Superinsulation Cooling channel (inside Cu block) ~ 8” Converter circuitry Cu thermal mass/mounting block Electrical feedthru Stainless steel tubes GHe vent LHe vendor’s dewar LHe

28. Cryostat for Measuring 100 W Circuits

29. 100 W SiGe Power Converter in Cryostat

30. SiGe 100 W Cryo Boost Converter Performance

31. Outline • The Team and Coordination • Goals & Applications • Technical Objectives & Approach • SiGe Cryo Power HBTs • SiGe Cryo Power Converters • Summary & Plans

32. 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 have begun development of SiGe semiconductor devices (HBTs and MOSFETs) for cryogenic power applications. • We have designed, fabricated, and used SiGe HBTs in power converters operating at cryogenic temperatures and converting >100 W.

33. Plans • Improve SiGe HBT characteristics (especially at cryo temps) • By simulation • On voltage • Off breakdown voltage • Switching speed • Compare power converter performance at cryogenic temperatures, comparing SiGe HBTs to Si BJTs • Design, fabricate and use SiGe MOSFETs in cryogenic power circuits • If practical, fabricate SiGe IGBTs