Novel SiGe Semiconductor Devices for Cryogenic Power Electronics ICMC/CEC August-September 2005 Keystone, Colorado

2 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary

3 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary

4 Rufus Ward, Bill Dawson, Lijun Zhu, Randall Kirschman GPD Optoelectronics Corp., Salem, New Hampshire Guofu Niu, Mark Nelms Auburn University, Dept. of Electrical and Computer Engineering, Auburn, Alabama Mike Hennessy, Eduard Mueller, Otward Mueller, MTECH Labs./LTE, Ballston Lake, New York Authors GPD Optoelectronics Corporation

5 Sponsors US Office of Naval Research US Army Aviation and Missiles Command Defense Advanced Research Projects Agency

6 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary

7 Goals Develop SiGe devices for cryogenic power use Exhibit the performance advantages of SiGe versus Si for cryogenic power Specifically: –Demonstrate prototype SiGe power diodes for cryogenic operation –Demonstrate a 100-W power conversion circuit, to deep cryogenic temperatures. –To ~ 55 K

8 Application Areas For power management and distribution (PMAD) –Power conversion for storage and distribution –Power conversion for motors/generators –E.g. “All-Electric” ship DoD applications –Cryogenic systems for ships and aerospace –Propulsion systems –Superconducting or cryogenic –Temperature ~ 60 – 65 K (for HTSC)

9 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary

10 Why SiGe? Can incorporate desirable characteristics of both Si and Ge Can optimize devices for cryogenic applications by selective use of Si and SiGe SiGe provides additional flexibility through band-gap engineering (% of Ge, grading) and selective placement All device types work at cryogenic temperatures –Diodes –Field-effect transistors –Bipolar transistors –Combinations of above (IGBTs, thyristors,...) Devices can operate at all cryogenic temperatures (as low as ~ 1 K if required) Compatible with conventional Si processing

11 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary

12 SiGe Diode Simulations

13 SiGe Heterostructure Diode (N+ backside implant) SiGe epilayer P+ Frontside contact Backside contact Si substrate N+ Si epilayer N–

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15 SiGe vs Si Diode Characteristics

16 SiGe vs Si Forward Voltage

17 SiGe vs Si and SiC Forward Voltage Univ. of Auburn measurements. SiGe

18 SiGe vs Si Reverse Recovery Univ. of Auburn measurements.

19 SiGe vs Si Reverse Recovery Univ. of Auburn measurements.

20 SiGe vs Si Reverse Recovery MTECH Labs. measurements.

21 SiGe vs Si Reverse Recovery MTECH Labs. measurements.

22 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary

23 SiGe Boost Converter Output capacitor SiGe diode Switching pulse Inductor Load SiGe HBT + – Input capacitor 24 V in 48 V out ~20 – 300 K Opto isolator Drive circuit Pulse generator Power supply + –

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

25 SiGe 100 W Cryo Boost Converter Backside

26 Cryostat for Measuring  100 W Circuits

W SiGe Power Converter in Cryostat

28 SiGe vs Si diodes in 100 W Cryo Boost Converter

29 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary

30 Summary Cryogenic power conversion is of interest for a range of applications within DoD 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 simulated SiGe diodes: results indicate improvements over Si diodes and have guided design. We have designed, fabricated, and used SiGe diodes (and HBTs) in power converters operating at cryogenic temperatures and converting >100 W.

31 Outline Authors and Sponsors Goals and Applications Why SiGe? Designs and results SiGe heterojunction diodes Cryogenic power converter Summary