NEPP - April/May 2002 Semiconductor Device Options for Low-Temperature Electronics
description
Transcript of NEPP - April/May 2002 Semiconductor Device Options for Low-Temperature Electronics
NEPP - April/May 2002
Semiconductor Device Options
forLow-Temperature Electronics
R. K. Kirschman, R. R. Ward and W. J. Dawson
GPD Optoelectronics Corp., Salem, New Hampshire
2
Topics
• Why low-temperature electronics?
• Semiconductor device behavior
• Semiconductor materials options
• Summary
3
Topics
• Why low-temperature electronics?
• Semiconductor device behavior
• Semiconductor materials options
• Summary
4
• Cold environment
Spacecraft for deep space/solar system
Why Low-Temperature Electronics?
5
Cold Spacecraft
• Eliminate heating, thermal control, isolation
• Reduce power, weight, size, cost, complexity
• Increase mission duration & capability
• Improve overall reliability
• Reduce disruption of environment
6
• Cold environment
Spacecraft for deep space & solar system
• Refrigeration provided for other hardware Space observatories Also superconducting/cryogenic motors & generators, power transmission lines, energy storage, cell-phone filters
Why Low-Temperature Electronics?
7
Observatories
• Cooling detectors for performance
• Signal-processing electronics (low-power) has been used since ~1980
• Drive (power) electronics for mechanical actuators & motors
8
Topics
• Why low-temperature electronics?
• Semiconductor device behavior
• Semiconductor materials options
• Summary
9
Semiconductor Devices
• Can operate at cryogenic temperatures, down to the lowest temperatures ~0 K
• All types– Minority & majority carrier– Bipolar & field-effect– Diodes, transistors
• Including power devices
• With appropriate materials and design
10
Characteristics at Cryogenic Temperatures
• Most characteristics improve - significantly– Gain (field-effect transistors)– On-voltage (field-effect transistors)– Losses & parasitic resistances– Leakage– Speed/frequency– Thermal conductivity – Also lower-loss passives (C, L)
11
Characteristics at Cryogenic Temperatures
• Most characteristics improve - significantly– Gain (field-effect transistors)– On-voltage (field-effect transistors)– Losses & parasitic resistances– Leakage– Speed/frequency– Thermal conductivity– Also lower-loss passives (C, L)
• Some characteristics degrade– P-N junction forward voltage– Breakdown voltage– Charge trapping (freeze-out, hot-electron
effects)
12
Topics
• Why low-temperature electronics?
• Semiconductor device behavior
• Semiconductor materials options
• Summary
13
Materials Options
• Elemental semiconductors– IV– Si, Ge, C (diamond)
• Compound semiconductors– IV-IV, III-V, (II-VI)– GaAs, GaP, InP, SiC, ... (large gap)– InSb, InAs, ... (small gap)
• Alloys (Elemental & Compound)– IV-IV, III-V, (II-VI)– SiGe– InGaAs, AlGaAs, ...
14
Elemental Semiconductors
• Si
– Widely available, vast technology base
– Power circuits demonstrated down to ~77 K, lower temperatures not demonstrated for power devices
– Majority devices (field-effect transistors) work at cryogenic temperatures
– Minority devices (bipolar transistors) lose performance upon cooling, not useable at cryogenic temperatures
15
Si Power Circuit Examples(selected)
Circuit/system Power Experimental Results Refs
Three-phase bridgeinverter
50 kW Loss ~1% at 77 K Gardiner’96
Class E RF (6.78 MHz)power amp
~1000 W Efficiency 85% @ 333 K (60°C) 99% @ ~90 K(loss 15% vs 1%)
Mueller‘93
Buck PWM dc-dcconverter
175 W Efficiency 95.8% 300 K 97% 77 K(loss 4.2% vs 3%)
Ray‘95
Boost PWM dc-dcconverter
150 W Efficiency 94% @ 300 K 95.9% @ 77 K Ray‘96
16
Elemental Semiconductors
• Ge
– Modest technology base
– Majority and minority devices work to ~20 K and lower
– Higher mobility than Si, room and low temperature
– Lower p-n junction V than Si or III-Vs
– Lower breakdown V
– Good gate insulator difficult (needed for MOS devices)
17
Mobility Comparison
Data from Madelung, 1991, pp. 18,34.
0
1 104
2 104
3 104
4 104
5 104
80 K 300 K
n-Sip-SiFn-Gep-Ge
np
p
p
p nn
n
Si
Si
Ge
Ge
18
Field-Effect Transistor Comparison
0
0.5
1
1.5
2
2.5
3
3.5
0 50 100 150 200 250 300
Temperature, T (K)
Si JFET (U310)
Ge JFET
Si JFET (2N4416)
I (300)dss
dss
I (T)
GaAs MESFET (3SK121)
19
Bipolar Junction Transistor Comparison
1
10
100
1000
01020304050
Temperature -1 (1000/K)
SiGe
20 30 50 80 300120
Temperature (K)
20
Ge Bipolar Junction Transistor
Zero: upper right Horiz: 0.5 V/div Vert: 1 mA/divIB: 0.02 mA/step at RT, 0.1 mA/step at 4 K
300 K 4 K
21
P-N Junction (Diode) Forward Voltage
0
0.5
1
1.5
0.2 A1 A
2 A4 A
0 40 80 120 160 200 240 280 320
Vf vs T Temperature (K)
Ge
Si
22
Compound Semiconductors
• GaAs, GaP, InP, SiC, InSb, InAs, ...– Medium technology base for GaAs– Minimal technology base for others– Good gate dielectric is difficult– Power devices not developed– Little information on cryogenic power
characteristics– Higher p-n junction forward V than Si or Ge– Breakdown - ?
23
Alloy Semiconductors• SiGe
– Extensive recent development and application for RF– Compatible with existing widely available Si
technology base– Design flexibility – band-gap engineering and
selective use– Minimal information on power device performance,
nothing on cryogenic power device performance
• InGaAs– Demonstrated to 20 K for power
• Other materials– Little or no information for cryogenic power devices
24
Topics
• Why low-temperature electronics?
• Semiconductor device behavior
• Semiconductor materials options
• Summary
25
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
• Si, Ge, SiGe are excellent candidates for cryogenic power devices, depending on temperature and other factors
26
Summary (cont’d)
• Use Si where possible– Extensive technology base and availability– Limitations for deep cryogenic temperatures– Several groups working on Si for low
temperature
• Develop Ge and SiGe– For deep cryogenic temperatures (to ~20 K)
and/or performance advantages– Ge being developed for cryogenic power– SiGe investigation just beginning
• Other materials, GaAs, InGaAs, ...– Also possible for cryogenic operation