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Ge Semiconductor Devices for Cryogenic Power Electronics - II

Ge Semiconductor Devices for Cryogenic Power Electronics - II. WOLTE 5. Grenoble, June 2002. R. R. Ward, W. J. Dawson, R. K. Kirschman GPD Optoelectronics Corp., Salem, New Hampshire O. Mueller LTE–Low Temperature Electronics, Ballston Lake, New York

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Ge Semiconductor Devices for Cryogenic Power Electronics - II

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  1. Ge Semiconductor DevicesforCryogenic Power Electronics - II WOLTE 5 Grenoble, June 2002

  2. R. R. Ward, W. J. Dawson, 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. HammoudDynacs Corp., Cleveland, Ohio

  3. Cryogenic Power Electronics • Semiconductor devices (diodes and transistors) • For Power Management and Actuator Control • For use down to 30 K (and lower) • Supported by NASA Glenn Research Center

  4. ApplicationsSpace • Solar-system exploration • Reasons: Cold environment, reduced power • For: Outer planets, cold satellites, interstellar • Scientific spacecraft/observatories • Reason: Cryogenic sensors and optics • For: Motors and actuators

  5. ApplicationsDefense, Industry, Commercial • Medical instruments (MRI) • Electrical power (superconducting electrical power storage, transmission, distribution) • Motors/generators (superconducting or cryogenic) • Magnetic confinement (superconducting or cryogenic) • High-power amplifiers (cell phone base stations, MRI)

  6. ApplicationsDefense, Industry, Commercial • Medical instruments (MRI) • Electrical power (superconducting electrical power storage, transmission, distribution) • Motors/generators (superconducting or cryogenic) • Magnetic confinement (superconducting or cryogenic) • High-power amplifiers (cell phone base stations, MRI) • Reasons: Improved efficiency and reliability, reduced size and mass; many systems already incorporate cryogenics

  7. ApplicationsSpace • Solar-system exploration • Reasons: Cold environment, reduced power • For: Outer planets, cold satellites, interstellar • Scientific spacecraft/observatories • Reason: Cryogenic sensors and optics • For: Motors and actuators

  8. Solar System Exploration • Rovers, fly-by, orbiters, landers, probes, penetrators • Cold environments • - Heating • - Wake/sleep (where possible)

  9. 1 2 HEATING POWER TEMPERATURE CONTROL 5 4 3 CRYOGENIC ELECTRONICS CONVENTIONAL ELECTRONICS COLD ENVIRONMENT Spacecraft

  10. “Cold” Spacecraft • Eliminate heating, thermal control, isolation • Reduce power, weight, size, cost, complexity • Improve overall reliability • Reduce disruption of environment • Increase mission duration & capability

  11. ApplicationsSpace • Solar-system exploration • Reasons: Cold environment, reduced power • For: Outer planets, cold satellites, interstellar • Scientific spacecraft/observatories • Reason: Cryogenic sensors and optics • For: Motors and actuators

  12. NGST - Next Generation Space TelescopeNASA Goddard Design ~30 K

  13. Why Ge Devices? • Ea,d (Ge) < Ea,d (Si)

  14. Why Ge Devices? • Ea,d (Ge) < Ea,d (Si)  Lower T for Ge

  15. Why Ge Devices? • Ea,d (Ge) < Ea,d (Si)  Lower T for Ge • Experience with Ge JFETs at cryogenic temperatures

  16. Why Ge Devices? • Ea,d (Ge) < Ea,d (Si)  Lower T for Ge • Experience with Ge JFETs at cryogenic temperatures • Ge has advantages over other semiconductor materials Higher mobility than Si (especially at low temp) • Lower p-n junction forward voltage than Si or III-Vs

  17. Mobility Comparison Data from Madelung, 1991, pp. 18,34.

  18. Why Ge Devices? • Ea,d (Ge) < Ea,d (Si)  Lower T for Ge • Experience with Ge JFETs at cryogenic temperatures • Ge has advantages over other semiconductor materials • Higher mobility than Si (especially at low temp) Lower p-n junction forward voltage than Si or III-Vs

  19. P-N Junction (Diode) Forward Voltage

  20. Why Ge Devices ? (cont’d) • Applications require operation to 30 - 40 K range • Ge devices of all types can operate to low cryogenic temperatures (~ 20 K or lower) Diodes can operate to deep cryogenic temperatures • JFETs can operate to deep cryogenic temperatures (down to few K) • Bipolar transistors can operate to deep cryogenic temperatures

  21. Results – 15-A Ge Diode

  22. Results – 15-A Ge Diode

  23. Results – 60-A Ge Diode

  24. Results – 60-A Ge Diode

  25. Why Ge Devices? (cont’d) • Applications require operation to 30 - 40 K range • Ge devices of all types can operate to low cryogenic temperatures (~ 20 K or lower) • Diodes can operate to deep cryogenic temperatures JFETs can operate to deep cryogenic temperatures (down to few K) • Bipolar transistors can operate to deep cryogenic temperatures

  26. Field-Effect Transistor Comparison

  27. Low-Power Ge JFET at 4 K

  28. Why Ge Devices? (cont’d) • Applications require operation to 30 - 40 K range • Ge devices of all types can operate to low cryogenic temperatures (~ 20 K or lower) • Diodes can operate to deep cryogenic temperatures • JFETs can operate to deep cryogenic temperatures (down to few K) Bipolar transistors can operate to deep cryogenic temperatures (down to ~20 K or lower)

  29. Ge Bipolar Junction Transistor 300 K 4 K Zero: upper right Horiz: 0.5 V/div Vert: 1 mA/div IB: 0.02 mA/step at RT, 0.1 mA/step at 4 K

  30. Ge Bipolar Junction Transistor

  31. Bipolar Junction Transistor Comparison

  32. Au/Cr electrode Si3N4 SiO2 Ge substrate Ge MIS Structures

  33. Results – Ge MIS Structures

  34. 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 have characterized Ge devices – diodes, JFETs, and bipolars – at cryogenic temperatures • Ge devices can operate to deep cryogenic temperatures – to 20 K and as low as 4 K

  35. Plans • Continue to evaluate and characterize Ge devices at cryogenic temperatures • Determine necessary design features for cryogenic power devices – for 30 K and lower • Develop related infrastructure • Fixturing and instrumentation for evaluation • Packaging and interconnections

  36. Plans (cont’d) • Design, fabricate and evaluate Ge power devices for cryogenic operation • Demonstrate Ge MOSFETs • Develop Ge cryogenic power devices: diodes, BJTs, JFETs, MOSFETs, IGBTs • Improve device characteristics (reverse breakdown voltage, for example) • Evaluate performance in power circuits. • Investigate SiGe devices for cryogenic power applications

  37. Results – Ge MIS Structures

  38. Reliability • Processes involving thermal energy effectively absent • Electromigration • Corrosion • Interdiffusion • Remaining reliability issues • Thermal expansion differences • Charge trapping/freeze-out • Reduce by materials selection, device design, operating conditions

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