SiGe Semiconductor Devices for Cryogenic Power Electronics

1. Electrochemical Society Seventh International Symposium on Low Temperature Electronics SiGe Semiconductor DevicesforCryogenic Power Electronics 14 October 2003, Orlando, Florida

2. R. R. Ward, W. J. Dawson, L. Zhu, R. K. Kirschman GPD Optoelectronics Corp., Salem, New Hampshire O. Mueller LTE–Low Temperature Electronics, Ballston Lake, New York R. L. Patterson, J. E. DickmanNASA Glenn Research Center, Cleveland, Ohio A. HammoudQSS Group Inc., Cleveland, Ohio Supported by NASA Glenn Research Center and ONR/DARPA

3. Why use SiGe?

4. Why SiGe Devices? • Si-Based Circuits Demonstrated, but only > 77 K • Standard Si Bipolar Devices Cease Operation < ~100 K • Applications Require Operation < 77 K, to ~30 – 40 K • Possible Materials for < 77 K are Ge and SiGe

5. Why SiGe Devices? • SiGe Devices Can Operate to Lowest Cryogenic Temperatures (~ 0 K) • All Device Types – Diodes, Field-Effect Transistors, Bipolar Transistors • Highly Compatible with Si Processing • Can Optimize Devices for Cryogenic Applications by Selective Use of Ge, Si, SiGe • SiGe Provides Additional Flexibility through Band-Gap Engineering (% of Ge)

6. Development Program

7. Development Program • Parameters • Low power (~10 W) to medium power (~100 W) • Temperature range 300 K to ~20 K • Past • Initial SiGe diodes fabricated • Initial SiGe heterojunction bipolars (HBTs) fabricated • Future • MOSFETs (lateral, vertical) • Power HBTs (vertical) • IGBTs (lateral, vertical)

8. SiGe Cryo Power Diodes

9. SiGe Cryo Power Diodes - Design P+ SiGe Metal N– Si epi N+ N+ Si Metal (N+ implant)

10. SiGe vs Si Power Diodes - Forward

11. SiGe vs Si Power Diodes - Forward

12. SiGe Cryo Power Diodes - Forward Voltage

13. SiGe Cryo Power Diodes - Forward

14. SiGe Cryo Power Diodes - Forward

15. SiGe Cryo Power Diodes - Forward Voltage

16. SiGe Cryo Power Diodes - Reverse

17. SiGe Cryo Power Diodes - Reverse

18. SiGe Cryo Power Diodes - Reverse Recovery

19. SiGe Cryo Power Diodes - Reverse Recovery

20. SiGe Cryo Power Diodes - Results • N on P and P on N, single and double epi • Measured to 77 K; operate to ~?? K • Forward V less than Si at low – med forward I • Imax ~> 10 A (300 – 77 K) • Reverse breakdown V >100 V (300 – 77 K) • Reverse recovery decreases at 77 K

21. SiGe Cryo Heterojunction Bipolar Transistors (HBTs)

22. Emitter contact Base contact ~ 0.5 μm n+ Si ~ 0.4 μm p SiGe ~ 20 μm n– Si ~ 300 μm n+ Si Collector contact SiGe Cryo Power HBTs - Design N-P-N (N+/P/N-/N+)

23. SiGe Cryo Power HBTs - 300 K

24. SiGe Cryo Power HBTs - 80 K

25. SiGe Cryo Power HBTs - 80 K

26. SiGe Cryo Power HBTs - 80 K

27. SiGe Cryo Power HBTs - 40 K

28. SiGe Cryo Power HBTs - 40 K

29. SiGe Cryo Power HBTs - Results • Initial fabrication • NPN • Operate down to ~40 K • Power ~5 W, limited by package • I max ~> 0.4 A (300 – 40 K) • V forward breakdown ~>30 V (300 – 40 K) • Need improved contacts

30. Cryo Power SiGe Devices - Plans • HBTs • Improve HBT contacts, extend operation to ~20 K • Larger area, I max to 10 A (300 – 20 K) • V forward breakdown >100 V (300 – 20 K) • High-power cryogenic packaging • Additional Devices • MOSFETs • IGBTs • Medium power, 300 – 20 K operation

31. Summary • Cryogenic power electronics is needed for spacecraft going to cold environments and for space observatories • Temperatures may be as low as ~30 – 40 K • We are developing SiGe devices specifically for cryogenic power applications • We have made initial SiGe cryo power diodes and HBTs • We plan to improve the diode and HBT characteristics and to develop MOSFETs and IGBTs