Novel SiGe Semiconductor Devices for Cryogenic Power Electronics

ICMC/CEC August-September 2005 Keystone, Colorado

Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 2

Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 3

Authors

GPD Optoelectronics Corporation

Rufus Ward, Bill Dawson, Lijun Zhu, Randall Kirschman GPD Optoelectronics Corp., Salem, New Hampshire Guofu Niu, Mark Nelms Auburn University, Dept. of Electrical and Computer Engineering, Auburn, Alabama Mike Hennessy, Eduard Mueller, Otward Mueller, MTECH Labs./LTE, Ballston Lake, New York 4

Sponsors

US Office of Naval Research US Army Aviation and Missiles Command Defense Advanced Research Projects Agency 5

Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 6

Goals

• Develop SiGe devices for cryogenic power use • Exhibit the performance advantages of SiGe versus Si for cryogenic power • Specifically: – Demonstrate prototype SiGe power diodes for cryogenic operation – Demonstrate a 100-W power conversion circuit, to deep cryogenic temperatures.

– To ~ 55 K 7

Application Areas

• For power management and distribution (PMAD) – Power conversion for storage and distribution – Power conversion for motors/generators – E.g. “All-Electric” ship • DoD applications – Cryogenic systems for ships and aerospace – Propulsion systems – Superconducting or cryogenic – Temperature ~ 60 – 65 K (for HTSC) 8

Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 9

Why SiGe?

• Can incorporate desirable characteristics of both Si and Ge • Can optimize devices for cryogenic applications by selective use of Si and SiGe • SiGe provides additional flexibility through band-gap engineering (% of Ge, grading) and selective placement • All device types work at cryogenic temperatures – Diodes – Field-effect transistors – Bipolar transistors – Combinations of above (IGBTs, thyristors, ...) • Devices can operate at all cryogenic temperatures (as low as ~ 1 K if required) • Compatible with conventional Si processing 10

Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 11

SiGe Diode Simulations

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SiGe Heterostructure Diode

SiGe epilayer P+ Si epilayer N – Si substrate N+ Frontside contact Backside contact (N+ backside implant)

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Wafer ID

50584G-J 50583G-J 50582F-J 50584A-F 50583A-F 50582A-E 1A 70305 1B 70307 2A 70295/7 (3A*) 70298 21** 22** 23** 24***

Si substrate

n-type, 10-50 ? -cm 1e14 cm 8e14 cm –3 p-type, 10-50 ? -cm –3 n-type, 1e19 cm p-type, 1e19 cm n-type, 1e19 cm n-type, 1e19 cm -3 -3 -3 -3

thickness(es) and composition Epilayer(s) dopant(s) First series (6 types)

22.1 nm, 19.5% Ge n-type, phosphorus 21.8 nm, 20.5% Ge 21.2 nm, 20.1% Ge 22.1 nm, 19.5% Ge 21.8 nm, 20.5% Ge p-type, boron undoped n-type, phosphorus p-type, boron 21.2 nm, 20.1% Ge undoped

Second series (4 types)

20.3 μm Si 30 nm, 31% Ge n-type, phosphorus p-type, boron 20.3 μm Si 30 nm, 31% Ge 20.3 μm Si 206 nm, 8% Ge 20.3 μm Si 300? nm, 5.3% Ge 500? nm p-type, boron n-type, phosphorus n-type, phosphorus p-type, boron n-type, phosphorus p-type, boron p-type, boron

Third series (4 types)

20 μm Si n-type

doping concentrations(s) (cm –3 )

1.8e19

1.6e19

undoped 1.8e19

1.6e19

undoped 7e14 6.5e18

5.2e14

1.1e19

6e14 1.5e19

6e14 3e17 1.3e19

Si, n+ > 3e19* Si, n+ > 3e19* 20 μm Si n-type uniform doping, 2e14 to 6e14 graded dopant concentration, ~1e15 at substrate to ~2e14 at SiGe epi layer Si, n+ > 3e19* 20 μm SiGe, graded Ge fraction: 0% Ge at substrate to 20% at SiGe p+ epi layer n-type uniform doping, 2e14 to 6e14 Si, n+ > 3e19* Si, 20 μm n-type uniform doping: 2e14 to 6e14Si, thickness same as above (~100 nm), p+ 1e19 *This wafer was specified for another type of device, but was also used for diodes.

**Epi layer 2: SiGe, 20%Ge, maximize thickness (~100 nm), p+ 1e19.

***Epi layer 2: Si, thickness same as above (~100 nm), p+ 1e19.

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SiGe vs Si Diode Characteristics

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SiGe vs Si Forward Voltage

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SiGe vs Si and SiC Forward Voltage

1400 1200 1000 800 600 400 200 0 -200 SiGe 50 SiC SiGe Si #1 Si #2 Si #3 -150 -100 -50

Temperature (degrees C)

0 Univ. of Auburn measurements.

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SiGe vs Si Reverse Recovery

Univ. of Auburn measurements.

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SiGe vs Si Reverse Recovery

Univ. of Auburn measurements.

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SiGe vs Si Reverse Recovery

MTECH Labs. measurements.

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SiGe vs Si Reverse Recovery

MTECH Labs. measurements.

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Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 22

24 V in + Power supply –

SiGe Boost Converter

Input capacitor Inductor SiGe HBT SiGe diode Output capacitor 48 V out + – Load Pulse generator Opto isolator Drive circuit Switching pulse ~20 – 300 K

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SiGe 100 W Cryo Boost Converter

100 kHz, 24 V in, 48 V out 24

SiGe 100 W Cryo Boost Converter

Backside 25

Cryostat for Measuring



100 W Circuits

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100 W SiGe Power Converter in Cryostat

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SiGe vs Si diodes in 100 W Cryo Boost Converter 28

Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 29

Summary

• Cryogenic power conversion is of interest for a range of applications within DoD and elsewhere.

• For cryogenic power conversion, SiGe devices are potentially superior to devices based on Si or Ge.

• We are developing SiGe semiconductor devices for cryogenic power applications.

• We have simulated SiGe diodes: results indicate improvements over Si diodes and have guided design.

• We have designed, fabricated, and used SiGe diodes (and HBTs) in power converters operating at cryogenic temperatures and converting >100 W.

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Outline

Authors and Sponsors Goals and Applications Why SiGe?

Designs and results SiGe heterojunction diodes Cryogenic power converter Summary 31