1. Ge Semiconductor Devices for Cryogenic Power Electronics - V
WOLTE 6
Ge Semiconductor Devices for Cryogenic Power Electronics - V
ESA/ESTEC, Noordwijk, June 2004

2. Supported by NASA Glenn Research Center
R. R. Ward, W. J. Dawson, L. Zhu, R. K. Kirschman GPD Optoelectronics Corp., Salem, New Hampshire
O. Mueller, M. J. Hennessy, E. K. Mueller
MTECH Laboratories, Ballston Spa, 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

3. “Very Little of the Solar System (or the Universe) Is at Room Temperature.”

4. Temperatures for Spacecraft

5. Solar System Exploration
Fly-by, orbiters, landers, rovers, probes, penetrators
Using conventional electronics in cold environments
- Heating
- Wake/sleep (where possible)

6. “Traditional” Spacecraft
COLD ENVIRONMENT
CONVENTIONAL
ELECTRONICS
HEATING/COOLING
SYSTEM
TEMPERATURE
CONTROL
THERMAL INSULATION
(HEAT STORAGE)

7. “Cold” Spacecraft
CRYOGENIC
ELECTRONICS
COLD ENVIRONMENT

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

9. Development Program

10. Cryogenic Power Electronics
Active semiconductor devices for power circuits
For spacecraft power management & actuator control
Parameters
Power ~10 W
Temperature range 300 K to ~20 K
Device types
Diodes (P--N, 10 A, 300 V)
JFETs (lateral, vertical)
MISFETs (lateral, vertical)
BJTs (vertical implanted)
Based on Ge

11. Why Use Ge?

12. Why Ge Devices? Applications require operation to 30 – 40 K range
Ge devices of all types can operate to low cryogenic temperatures (~20 K or lower)
Diodes
Field-effect transistors (JFETs, MISFETs)
Bipolar transistors
Performance advantages
P-N junction voltages are low
Mobility is high

13. Ge Cryo Power Diodes

14. Ge Cryo Power Diodes P- - N Bulk Design
Metal
P+ implant
Guard ring(s)
N– ( )
Metal
N+ implant

15. Ge Diode - Forward I-V

16. Ge Diode - Forward I-V

17. Ge Diode - Forward I-V

18. Ge Diodes - Forward Voltage
Si data from literature

19. Ge Diodes - Forward Voltage
Si data from literature

20. Ge Diodes - Reverse Breakdown

21. Ge Diodes - Reverse Recovery

22. Ge Diodes - Reverse Recovery

23. Ge Diodes - Reverse Recovery

24. Ge Cryo Power Field-Effect Transistors

25. Ge Cryo Power JFET or MISFET
~1.3 mm G S D

26. Ge Cryo Power JFETs (Junction Field-Effect Transistors)

27. Ge JFET Cross-Section (n-channel)
Back gate contact
Source
Front gate
P+ implant
P+ substrate
N epitaxial layer
N+ implant
Drain

28. Ge JFET at 300 K (n-channel)
ΔVGS = 1 V/step J
10 V

29. Ge JFET at 77 K (n-channel)
ΔVGS = 1 V/step
10 V

30. Ge JFET at 4 K (n-channel)
ΔVGS = 1 V/step
10 V

31. Ge JFET at 300 K (p-channel)
ΔVGS = 1 V/step
JL2-01B-Q01, Quad JFET
50 V

32. Ge JFET at 77 K (p-channel)
ΔVGS = 1 V/step
50 V

33. Ge JFET at 4 K (p-channel)
ΔVGS = 1 V/step
50 V

34. Ge JFET Cross-Section (p-channel)
Back gate contact
Source
(N+ implant)
N+ substrate
P epitaxial layer
P+ implant
Drain
Trench

35. Ge JFET at 300 K (p-channel)
ΔVGS = 2 V/step
JL2-01B-Q01, Quad JFET
20 V

36. Ge JFET at 77 K (p-channel)
ΔVGS = 2 V/step
20 V

37. Ge JFET at 4 K (p-channel)
ΔVGS = 2 V/step
20 V

38. Ge Cryo Power MISFETs (Metal-Insulator-Semiconductor Field-Effect Transistors)

39. Lateral Ge MISFET Design (n-channel)
Substrate contact
Source
Gate
(P+ implant)
P substrate
Gate dielectric
N+ implant
Drain

40. Ge MISFET at 300 K (n-channel)
ΔVGS = 1 V/step
M31
20 V

41. Ge MISFET at 77 K (n-channel)
ΔVGS = 1 V/step
20 V

42. Ge MISFET at 4 K (n-channel)
ΔVGS = 1 V/step
20 V

43. Ge MISFET Switching - 50 kHz
~30 W Load

44. Ge MISFET Switching - 5 MHz
~30 W Load

45. Ge MISFET at 300 K (p-channel)
ΔVGS = 2 V/step
M31
20 V

46. Ge MISFET at 77 K (p-channel)
ΔVGS = 2 V/step
20 V

47. Ge MISFET at 4 K (p-channel)
ΔVGS = 2 V/step
20 V

48. Vertical Ge MISFET Design (n-channel)
Drain
Source
Gate
P+ implant
P– substrate
Gate dielectric
N epi

49. Ge Vertical MISFET at 77 K (n-channel)
ΔVGS = 2 V/step
10 V

50. Ge Bipolar Junction Transistors

51. Ge Bipolar – Double-Implant, Vertical
Emitter
Base
N+ implant
P implant
N– substrate
Collector
N+ implant

52. Ge BJT at 77 K (npn)
ΔIB = 1 mA/step
0.1 A
10 V

53. Ge BJT at 77 K (pnp)
ΔIB = 2 mA/step
0.05 A
100 V

54. Summary
Cryogenic power electronics is needed for spacecraft going to cold environments and for space observatories
Temperatures may be as low as ~ K
Used Ge
Ge devices of all types can operate to deep cryogenic temperatures – to 20 K, as low as 4 K
We developed Ge diodes, JFETs, MISFETs, BJTs specifically for cryogenic power applications
Power to ~20 W

55. Continuing Development
Now developing cryogenic power devices based on SiGe
Flexibility, compatibility, easier dielectric
Two separate programs: NASA (spacecraft) and DARPA (motors & generators using superconductors)
Temperature ranges: to ~20 K (NASA, medium power) and ~55 K (DARPA, higher power)
HBTs, MOSFETs, IGBTs (NASA); diodes, thyristors (DARPA)
Simulation, fabrication, evaluation
Demonstrations of SiGe devices in ~ W power converters at cryogenic temperatures