LSA Diodes breaking the 1f 2 power law

LSA Diodes (breaking the 1/f 2 power law for semiconductor electronic devices) in Honor of Prof. Lester F. Eastman Cornell University Prof. John A. Copeland ECE Georgia Tech

The LSA Era: 1964 -69 Transistors started to replace Vacuum Tubes in audio, then RF applications. Long distance (intercity) telephone voice traffic and network TV, carried by microwave radio relay towers. Microwave circuits required travelingwave and close-spaced vacuum tubes, expensive and unreliable. Viet Nam War (radar uses magnetron tubes for high pulse power). Needed: microwave semiconductor devices.

n-Ga. As Oscillator Time Line 1957 1961 1962 1963 1964 Eastman - receives Ph. D. , joins Cornell faculty. Ridley and Watson's paper on negative resistance in solids C. Hilsum's paper on transferred-electron amplifier, oscillators J. B Gunn (IBM) shows moving electric-field in n-Ga. As Eastman starts research on compound semiconductors (Ga. As, Gunn-effect, high power pulses for radar) 1965 Copeland - receives Ph. D. , joins Bell Labs in Murray Hill, NJ (Ga. As, Gunn-effect, continuous power for communications) 1966 Mc. Cumber & Chenoweth's computer simulation of Gunn osc. 1967 Copeland - computer simulations show a resonant circuit can cause a n-Ga. As diode to oscillate (LSA mode) at much higher frequency with similar power - theory says n/f critical, not length. 1967 Eastman and Copeland travel to conference in Bad Neuheim, and visit Munich, London, Royal Radar Establishment 1967 Copeland - produced 20 m. W continuous at 88 GHz. 1967 Keith Kennedy and Eastman produced high power pulses with LSA Oscillators (350 watts at 8 GHz). 1970 Copeland receives IEEE Morris Liebmann Award for LSA

velocity E < 3000 v/cm: d. E d. V E > 3000 v/cm: Mobility = d. V/d. E Carrier drift velocity (107 cm/s) Electric Field (k. V/cm) Electron drift velocity vs. electric field in n-type Ga. As. The ac (differential) resistance is negative for E > 3000 v/cm Why? Brian Ridley may explain in a few minutes.

v=107 cm/s f = v/L n-Ga. As Diode from ingot 10 -micron epitaxial layer

For LSA (Limited Space Charge) operation, the electric field must dip for a portion of each cycle into the positive mobility region, to quench any space charge that has begun to accumulate. from "Gunn-Effect Devices", B. G. Bosch and R. W. Engelmann, John Wiley &Sons, NY (c. 1970)

Frequency x Length (cm/s) Modes of Operation Carrier Density x Length

Gunn Diode P=a/f 2 - Kennedy and Eastman 350 W @ 8 GHz

Handheld LSA mm-wave Doppler Radar Profilometer Audio Headset 3 v R RF LSA diode in waveguide to antenna.

1968 to 2008 - Where did the research lead? At Cornell: more coming later in this program. At Bell Labs: 1968 - Because of the possibility of having mmwave semiconductor devices, development of a guided millimeter-wave system began. 1971 - Corning gave Bell Labs a piece of optical fiber to analyze, and the guided mm-wave system development was stopped before going into manufacture. Device research turned to Ga. As lasers, and long-wavelength lasers and photodetectors for 1. 3 to 1. 5 micron wavelengths.

1980 Experience working with Ga. As, and later mixed 3 -5 compounds (e. g. , Gax. Al 1 -x. Asy. P 1 -y), led to LEDs and lasers for lightwave systems.

References to my papers, which have references to the work of many others who contributed to this field. www. csc. gatech. edu/copeland/ These slides, old Spectrum and Electronics articles www. csc. gatech. edu/copeland/jac/LSA/ Email: jcopeland@ece. gatech. edu Alternate URL: users. ece. gatech. edu/copeland/jac/LSA/