Ge Semiconductor Devices for Cryogenic Power Electronics - V WOLTE 6 Ge Semiconductor Devices for Cryogenic Power Electronics - V ESA/ESTEC, Noordwijk, June 2004

Supported by NASA Glenn Research Center R. R. Ward, W. J. Dawson, L. Zhu, R. K. Kirschman GPD Optoelectronics Corp., Salem, New Hampshire O. Mueller, M. J. Hennessy, E. K. Mueller MTECH Laboratories, Ballston Spa, 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

“Very Little of the Solar System (or the Universe) Is at Room Temperature.”

Temperatures for Spacecraft

Solar System Exploration Fly-by, orbiters, landers, rovers, probes, penetrators Using conventional electronics in cold environments - Heating - Wake/sleep (where possible)

“Traditional” Spacecraft COLD ENVIRONMENT CONVENTIONAL ELECTRONICS HEATING/COOLING SYSTEM TEMPERATURE CONTROL THERMAL INSULATION (HEAT STORAGE)

“Cold” Spacecraft CRYOGENIC ELECTRONICS COLD ENVIRONMENT

“Cold” Spacecraft Benefits Eliminate heating, thermal control, isolation Reduce power, weight, size, cost, complexity Improve overall reliability Reduce disruption of environment Increase mission duration & capability

Development Program

Cryogenic Power Electronics Active semiconductor devices for power circuits For spacecraft power management & actuator control Parameters Power ~10 W Temperature range 300 K to ~20 K Device types Diodes (P--N, 10 A, 300 V) JFETs (lateral, vertical) MISFETs (lateral, vertical) BJTs (vertical implanted) Based on Ge

Why Use Ge?

Why Ge Devices? Applications require operation to 30 – 40 K range Ge devices of all types can operate to low cryogenic temperatures (~20 K or lower) Diodes Field-effect transistors (JFETs, MISFETs) Bipolar transistors Performance advantages P-N junction voltages are low Mobility is high

Ge Cryo Power Diodes

Ge Cryo Power Diodes P- - N Bulk Design Metal P+ implant Guard ring(s) N– ( ) Metal N+ implant

Ge Diode - Forward I-V

Ge Diode - Forward I-V

Ge Diode - Forward I-V

Ge Diodes - Forward Voltage Si data from literature

Ge Diodes - Forward Voltage Si data from literature

Ge Diodes - Reverse Breakdown

Ge Diodes - Reverse Recovery

Ge Diodes - Reverse Recovery

Ge Diodes - Reverse Recovery

Ge Cryo Power Field-Effect Transistors

Ge Cryo Power JFET or MISFET ~1.3 mm G S D

Ge Cryo Power JFETs (Junction Field-Effect Transistors)

Ge JFET Cross-Section (n-channel) Back gate contact Source Front gate P+ implant P+ substrate N epitaxial layer N+ implant Drain

Ge JFET at 300 K (n-channel) ΔVGS = 1 V/step J42 2004-01 10 V

Ge JFET at 77 K (n-channel) ΔVGS = 1 V/step 10 V

Ge JFET at 4 K (n-channel) ΔVGS = 1 V/step 10 V

Ge JFET at 300 K (p-channel) ΔVGS = 1 V/step JL2-01B-Q01, Quad JFET 50 V

Ge JFET at 77 K (p-channel) ΔVGS = 1 V/step 50 V

Ge JFET at 4 K (p-channel) ΔVGS = 1 V/step 50 V

Ge JFET Cross-Section (p-channel) Back gate contact Source (N+ implant) N+ substrate P epitaxial layer P+ implant Drain Trench

Ge JFET at 300 K (p-channel) ΔVGS = 2 V/step JL2-01B-Q01, Quad JFET 20 V

Ge JFET at 77 K (p-channel) ΔVGS = 2 V/step 20 V

Ge JFET at 4 K (p-channel) ΔVGS = 2 V/step 20 V

Ge Cryo Power MISFETs (Metal-Insulator-Semiconductor Field-Effect Transistors)

Lateral Ge MISFET Design (n-channel) Substrate contact Source Gate (P+ implant) P substrate Gate dielectric N+ implant Drain

Ge MISFET at 300 K (n-channel) ΔVGS = 1 V/step M31 20 V

Ge MISFET at 77 K (n-channel) ΔVGS = 1 V/step 20 V

Ge MISFET at 4 K (n-channel) ΔVGS = 1 V/step 20 V

Ge MISFET Switching - 50 kHz ~30 W Load

Ge MISFET Switching - 5 MHz ~30 W Load

Ge MISFET at 300 K (p-channel) ΔVGS = 2 V/step M31 20 V

Ge MISFET at 77 K (p-channel) ΔVGS = 2 V/step 20 V

Ge MISFET at 4 K (p-channel) ΔVGS = 2 V/step 20 V

Vertical Ge MISFET Design (n-channel) Drain Source Gate P+ implant P– substrate Gate dielectric N epi

Ge Vertical MISFET at 77 K (n-channel) ΔVGS = 2 V/step 10 V

Ge Bipolar Junction Transistors

Ge Bipolar – Double-Implant, Vertical Emitter Base N+ implant P implant N– substrate Collector N+ implant

Ge BJT at 77 K (npn) ΔIB = 1 mA/step 0.1 A 10 V

Ge BJT at 77 K (pnp) ΔIB = 2 mA/step 0.05 A 100 V

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 Used Ge Ge devices of all types can operate to deep cryogenic temperatures – to 20 K, as low as 4 K We developed Ge diodes, JFETs, MISFETs, BJTs specifically for cryogenic power applications Power to ~20 W

Continuing Development Now developing cryogenic power devices based on SiGe Flexibility, compatibility, easier dielectric Two separate programs: NASA (spacecraft) and DARPA (motors & generators using superconductors) Temperature ranges: to ~20 K (NASA, medium power) and ~55 K (DARPA, higher power) HBTs, MOSFETs, IGBTs (NASA); diodes, thyristors (DARPA) Simulation, fabrication, evaluation Demonstrations of SiGe devices in ~100 - 1000 W power converters at cryogenic temperatures