SiGe Semiconductor Devices for Cryogenic Power Electronics Electrochemical Society Seventh International Symposium on Low Temperature Electronics SiGe Semiconductor Devices for Cryogenic Power Electronics 14 October 2003, Orlando, Florida

A. Hammoud QSS Group Inc., Cleveland, Ohio R. R. Ward, W. J. Dawson, L. Zhu, R. K. Kirschman GPD Optoelectronics Corp., Salem, New Hampshire O. Mueller LTE–Low Temperature Electronics, Ballston Lake, 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 and ONR/DARPA

Why use SiGe?

Why SiGe Devices? Si-Based Circuits Demonstrated, but only > 77 K Standard Si Bipolar Devices Cease Operation < ~100 K Applications Require Operation < 77 K, to ~30 – 40 K Possible Materials for < 77 K are Ge and SiGe

Why SiGe Devices? SiGe Devices Can Operate to Lowest Cryogenic Temperatures (~ 0 K) All Device Types – Diodes, Field-Effect Transistors, Bipolar Transistors Highly Compatible with Si Processing Can Optimize Devices for Cryogenic Applications by Selective Use of Ge, Si, SiGe SiGe Provides Additional Flexibility through Band-Gap Engineering (% of Ge)

Development Program

Development Program Parameters Past Future Low power (~10 W) to medium power (~100 W) Temperature range 300 K to ~20 K Past Initial SiGe diodes fabricated Initial SiGe heterojunction bipolars (HBTs) fabricated Future MOSFETs (lateral, vertical) Power HBTs (vertical) IGBTs (lateral, vertical)

SiGe Cryo Power Diodes

SiGe Cryo Power Diodes - Design Metal P+ SiGe N– Si epi N+ Si N+ Metal (N+ implant)

SiGe vs Si Power Diodes - Forward

SiGe vs Si Power Diodes - Forward

SiGe Cryo Power Diodes - Forward Voltage Si data from literature Ge data is for conventional commercial devices (for RT use)

SiGe Cryo Power Diodes - Forward

SiGe Cryo Power Diodes - Forward

SiGe Cryo Power Diodes - Forward Voltage Si data from literature Ge data is for conventional commercial devices (for RT use)

SiGe Cryo Power Diodes - Reverse

SiGe Cryo Power Diodes - Reverse

SiGe Cryo Power Diodes - Reverse Recovery

SiGe Cryo Power Diodes - Reverse Recovery

SiGe Cryo Power Diodes - Results N on P and P on N, single and double epi Measured to 77 K; operate to ~?? K Forward V less than Si at low – med forward I Imax ~> 10 A (300 – 77 K) Reverse breakdown V >100 V (300 – 77 K) Reverse recovery decreases at 77 K

SiGe Cryo Heterojunction Bipolar Transistors (HBTs)

SiGe Cryo Power HBTs - Design ~ 0.5 μm n+ Si ~ 0.4 μm p SiGe ~ 20 μm n– Si Emitter contact ~ 300 μm n+ Si Collector contact Base contact N-P-N (N+/P/N-/N+)

SiGe Cryo Power HBTs - 300 K

SiGe Cryo Power HBTs - 80 K

SiGe Cryo Power HBTs - 80 K

SiGe Cryo Power HBTs - 80 K

SiGe Cryo Power HBTs - 40 K

SiGe Cryo Power HBTs - 40 K

SiGe Cryo Power HBTs - Results Initial fabrication NPN Operate down to ~40 K Power ~5 W, limited by package I max ~> 0.4 A (300 – 40 K) V forward breakdown ~>30 V (300 – 40 K) Need improved contacts

Cryo Power SiGe Devices - Plans HBTs Improve HBT contacts, extend operation to ~20 K Larger area, I max to 10 A (300 – 20 K) V forward breakdown >100 V (300 – 20 K) High-power cryogenic packaging Additional Devices MOSFETs IGBTs Medium power, 300 – 20 K operation

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 We are developing SiGe devices specifically for cryogenic power applications We have made initial SiGe cryo power diodes and HBTs We plan to improve the diode and HBT characteristics and to develop MOSFETs and IGBTs