GeBased Semiconductor Devices for Cryogenic Power Electronics

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Ge-Based Semiconductor Devices forCryogenic
Power Electronics

• NEPP 2002

Houston, April/May 2002
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R. R. Ward, W. J. Dawson, R. K. Kirschman GPD
Optoelectronics Corp., Salem, New
Hampshire O. Mueller LTELow Temperature
Electronics, Ballston Lake, New York R. L.
Patterson, J. E. DickmanNASA Glenn Research
Center, Cleveland, Ohio A. HammoudDynacs Corp.,
Cleveland, Ohio
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Cryogenic Power Electronics

• Semiconductor Devices (diodes and transistors)
• For Power Management and Actuator Control
• For Use down to 30 K and Lower

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ApplicationsSpace

• Solar-System Exploration
• Reasons Cold environment, reduced power
• For Outer planets, cold satellites,
  interstellar
• Scientific Spacecraft
• Reason Cryogenic sensors and optics
• For Motors and actuators
• Long-Term Surface Installations
• Reasons Cold environment, reduced power
• For Outer planets, cold satellites

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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 (Base Stations, MRI)
• Reasons Improved efficiency and reliability,
  reduced size and mass many systems already
  incorporate cryogenics

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Why Ge and SiGe Devices?

• Si-Based Circuits Demonstrated, but only gt 77 K
• Si Bipolar Devices Cease Operation lt 100 K
• Applications Require Operation lt 77 K
• Other Materials (III-Vs) Uncertain for lt 77 K
• Possible Materials for lt 77 K are Ge and SiGe

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Why Ge and SiGe Devices?

• Can Optimize Devices for Cryogenic Applications
  by Selective Use of Ge, Si, SiGe
• SiGe Provides Additional Flexibility through
  Band-Gap Engineering ( of 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

• Present
• Characterize Ge devices at cryogenic temperatures
• Design and fabricate Ge diodes, MIS structures
  and transistors (BJT, JFET, MOSFET, IGBT)
• Low-power and medium-power for cryogenic
  operation
• Work with users and their applications
• Projected
• Design, fabricate and characterize SiGe devices
  for cryogenic power applications

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Ge JFET Cross-Section (n-channel)
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Low-Power Ge JFET at 4 K
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Results 15-A Ge Diode
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Results 15-A Ge Diode
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Results 60-A Ge Diode
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Results 60-A Ge Diode
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Ge vs Si Power Diodes Forward
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Ge Power Diodes Breakdown
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Ge MIS Structures
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Results Ge MIS Structures
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Results Ge MIS Structures
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Results Ge Bipolar Transistor
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Bipolars Cryogenic Temperatures
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Summary

• 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
• Ge MIS Structures Have Been Demonstrated and
  Characterized at Room and Cryogenic Temperatures
• Preliminary SiGe MIS Structures Have Been Made

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Plans

• Improve Device Characteristics (Reverse
  Breakdown Voltage, for example)
• Demonstrate Ge MOSFETs
• Determine Necessary Design Features for
  Cryogenic Power Devices for 30 K and lower
• Develop Ge Cryogenic Power Devices
  Diodes, BJTs, JFETs, MOSFETs, IGBTs
• Propose Investigation and Development of
  SiGe Cryogenic Power Devices