Ge Semiconductor Devices for Cryogenic Power Electronics IV

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Ge Semiconductor DevicesforCryogenic Power
Electronics - IV

• Electrochemical Society
• Seventh International Symposium on Low
  Temperature Electronics

14 October 2003, Orlando, Florida
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R. R. Ward, W. J. Dawson, L. Zhu, R. K.
Kirschman GPD Optoelectronics Corp., Salem, New
Hampshire M. J. Hennessy, E. K. Mueller MTECH
Laboratories, Ballston Lake, New York R. L.
Patterson, J. E. DickmanNASA Glenn Research
Center, Cleveland, Ohio A. HammoudQSS Group
Inc., Cleveland, Ohio
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Cryogenic Power Electronics

• Semiconductor Devices (diodes and transistors)
• For Use down to 30 K and Lower
• For Power Management and Actuator Control
• For Spacecraft
• Supported by NASA Glenn Research Center

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Why Use Ge?
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Why Ge Devices?

• Si-Based Circuits Demonstrated, but only gt 77 K
• Si Bipolar Devices Cease Operation lt 100 K
• Applications Require Operation lt 77 K, to 30
  40 K
• Possible Materials for lt 77 K are Ge and SiGe
• Ge Devices Can Operate to Lowest Cryogenic
  Temperatures ( 0 K)
• All Device Types Diodes, Field-Effect
  Transistors, Bipolar Transistors

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Development Program
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Development Program

• Parameters
• Low power (10 W) and medium power (100 W)
• Temperature range 300 K to 20 K
• Past
• Investigated existing Ge semiconductor devices
  at cryogenic temperatures (diodes, BJTs, JFETs)
• Designed and fabricated Ge cryogenic power
  diodes (P-?-N, 10 A, 300 V)
• Devices under Development
• MISFETs (lateral, vertical implanted, vertical
  epi)
• JFETs (lateral, vertical)
• BJTs (vertical implanted, vertical epi)
• IGBTs (vertical implanted, vertical epi)

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Ge Cryo Power Diodes
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Ge Cryo Power DiodesP-? - N Bulk Design
P implant
Metal
Guard ring(s)
N (? )
N implant
Metal
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Ge Cryo Power Diodes - Forward Voltage
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Ge Cryo Power Diodes - Forward Voltage
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Ge Cryo Power Diodes - Forward I-V
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Ge Cryo Power Diodes - Forward I-V
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Ge Cryo Power Diode Forward I-V
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Ge Power Diodes Reverse Breakdown
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Ge Power Diodes Reverse Recovery
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Ge Power Diodes Reverse Recovery
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Ge Power Diodes Reverse Recovery
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Ge Power Diodes Reverse Recovery
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Ge Power Diodes Reverse Recovery
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Ge Cryo Power Diodes - Future

• Improved Guard-Ring Designs and Tailored Implant
• Higher Vr
• Schottky Designs
• Lower forward voltage
• N-?-P (compared to P-?-N)
• Possible improvement in Vf and Vr
• Possible improvement in speed/reverse recovery
• Possible elimination of backlash at 4 K
• Possible lower reverse leakage

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Ge Cryo Power MISFETs
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Ge Cryo Power JFET or MISFET
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Basic Lateral Ge MISFET Design
Source
Gate dielectric
Gate
Drain
N implant
P substrate
Substrate
P implant
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Ge Power MISFET at 300 K
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Ge Power MISFET at 77 K
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Ge Power MISFET at 4 K
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Basic Vertical Ge MISFET Design
Two versions double-implant (above) and epi
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Basic Vertical Ge MISFET Design
Two versions double-implant and epi (above)
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Ge Cryo Power MISFETs - Plans

• Larger-Area and Modified Doping (for Lateral Ge)
• Higher I and higher Vbk
• Vertical Designs for Ge
• Higher I and higher Vbk
• Reverse Double-Implant Vertical Design for Ge
• Better results than present double-implant design

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Ge Cryo Power JFETs
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Ge JFET Cross-Section (n-channel)
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Power Ge JFET at 300 K
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Power Ge JFET at 77 K
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Power Ge JFET at 4 K
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Another Power Ge JFET at 20 K
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Power JFETs - Plans

• P-Type
• Complementary circuits
• Higher I and Vbk
• Vertical (SIT) Design
• Higher I and higher Vbk

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Ge CryoBipolar Junction Transistors
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Ge Bipolar Double-Implant
Emitter
N implant
Base
P implant
N substrate
Collector
N implant
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Ge Bipolar Epitaxial
Emitter
N implant
Base
P epi
N substrate
Collector
N implant
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Power BJTs - Plans

• Reverse Double-Implant Design for Ge
• Better characteristics than present
  double-implant design?
• Epitaxial Design for Ge

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Ge Cryo IGBTs
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Basic Ge IGBT Design
Two versions double-implant (above) and epi
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Basic Ge IGBT Design
Two versions double-implant and epi (above)
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Summary

• We Have Characterized Commercial Ge Devices
  (Diodes and Bipolars) at Cryogenic Temperatures
• In a Separate Development We Have Demonstrated
  that Ge JFETs Work Well at Cryogenic
  Temperatures
• All Types of Ge Devices Can Operate to Deep
  Cryogenic Temperatures to 20 K, as Low as 4 K
• Developed 10-A Ge Cryogenic Power Diodes with
  High Reverse Breakdown and Low Forward Voltage

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Summary contd

• Characterized Ge MIS Structures at Room and
  Cryogenic Temperatures
• Made Ge Power MISFETs that Operate from Room
  Temperature down to 4 K
• Made Ge Power JFETs that Operate from Room
  Temperature down to 4 K
• Improved MISFETs and JFETs Are in Progress
• Ge BJT and IGBT Fabrication Is in Progress