SOLID-STATE DEVICE RESEARCH CONFERENCE 69 1

The mesa units are mounted junction side down onto a gold-plated copper heat sink. To date the double-epitaxial diodes have reproducibly delivered between 0.3 watt and 0.7 watt CW in X-band with effi- ciencies between 5 percent and 7 percent. The efficiency is relatively independent of current density, in contradistinction to the conventional diffused silicon avalanche diodes. This performance is believed to be characteristic of the full and ready depletion associated with the abrupt n-n+ interface.

The physical realization of the abrupt theoretical model should allow optimization of performance and aid in clarifying some of the remaining anomalies. 6 ) A New Theory for Carrier-Field Inter-

actions and Electromagnetic Radiation in High-Frequency Avalanche Devices- R. I. Harrison, H. Berger, and S. P. Denker, General Telephone and Electronics Laboratories.

7) Transverse Negative Differential Mo- bility for Hot Electrons and Domain Formation in n-Type Germanium- M. Shyam, Fairchild Semiconductor, Research and Development Laboratory. Samples of a special split electrode geom-

etry were cut from (110) wafers of antimony doped germanium (resistivity 1-4 ohm. cm) with the longitudinal device axis coinciding with the (110) direction within 3”. On apply- ing a pulsed bias field nominal in the range 4-10 kV/cm, a transverse voltage appeared between two transverse electrodes whose polarity could be changed by introducing a small transverse electric field via a trimming potentiometer. The transverse polarization switching phenomena disappeared when the longitudinal field exceeded 10 kV/cm.

Measurements were made by probing the transverse electrodes along the device axis. These experiments show that the transverse polarization traverses along the axis of the device with a velocity of 8x106 cm/s. On cooling the samples to 77”K, it was found that the effect persisted in the longitudinal field range 1.5-4 kV/cm. The transverse polarization increased by about 50 percent.

Differences in surface preparation did not appear to have any influence on the effect. We were not able to detect the phe- nomena in any direction other than (110), or in higher resistivity material.

GENERAL SESSION Chairman: B. C. DeLoach, ‘Bell Telephone

Laboratories Organizer: F. M. Smits, Bell Telephone

Laboratories Opening remarks: W. Brittin, Acting Dean of

the Graduate School 1) Low-Frequency High-Efficiency Oscilla-

tions in Germanium IMPATT Diodes- R. L. Johnston and D . L. Scharfetter, Bell Telephone Laboratories, Inc. Pulsed operation of Germanium ava-

lanche diodes has produced oscillations from 10 MHz to 19 GHz, with efficiencies exceed-

3 GHz. ing 40 percent for frequencies between 2 and

The diodes are epitaxial diffused junction vz-p-p+ mesa structures, with depletion

widths -5 microns and breakdown voltages -60 volts. Typical diode area is 2 x lO-4cm2 and input power 20 watts for 10-100 ns. The usual IMPATT mode would be expected between 6 and 10 GHz.

Operation a t frequencies below the IM- PATT frequency requires circuit conditions suitable for IMPATT oscillations to be present to initiate the lower frequency, higher efficiency mode. This mode is char- acterized by a sudden decrease in diode volt- age and simultaneously increase in current, similar to that reported for silicon devices.20 The voltage may drop to a fraction of the breakdown value and the current increase with an order of magnitude. The static I-V curves, obtained with circuit conditions which do not permit any oscillations, ex- hibits positive incremental resistance in

distribution. agreement with theory for uniform current

Reproducible current and voltage wave- forms have been recorded for three dis- tinctly different low-frequency modes of operation, which result only from changes in the ac circuit seen by the diode.

1) The change in conduction state of the diode (drop in voltage, increase in current) is not followed by any low-frequency (sub- IMPATT) oscillations, and the resultant static I-V curve has very low (perhaps negative) incremental resistance.

2) High-efficiency moderate frequency (2-3 GHz) nearly sinusoidial oscillations.

3) Low-frequency (100 MHz-1GHz) oscillations which have an envelope of IM- PATT frequency oscillations. CW operation of the high efficiency mode has been achieved with liquid NZ cooling of the heat sink.

2) Computer Simulation of Low-Fre- quency High-Efficiency Oscillations in Germanium IMPATT Diodes-D. L. Scharfetter, D . J . Bartelink, and R. L. Johnston, Bell Telephone Laboratories, Inc. Diode structures whose experimental

characteristics are reported in another paper21 have produced similar current and voltage wave forms by computer simula- tion. The doping profile and circuit environ- ment of the simulated diodes matched the experimental units as closely as possible.

In a computer simulation of diode and circuit the following events are observed to happen. IMPATT oscillations build up un- til the generated charge increases the elec- tric field in front of the charge pulse suffi- ciently to produce a generation region which sweeps completely through the depletion re- gion to the substrate. Generated carrier space charge following behind the extended avalanche region reduces the electric field here to very low values (-200 V/cm). A trapped plasma of electrons and holes is ob- tained in the low-field region, with a re- sultant drop in diode voltage essentially to zero. The trapped plasma is extracted a t a

“High-power. high-efficiency silicon’ avalanche diodes 20 H. J. Prager. K. K. N. Chang and S. Weisbrod

a t ultra high frequencies.” PYOC. IEEE (Lellevs), vol. 55, p. 586-587, April 1967.

quency high eFciency oscillations in germanium IM- P’ R. L. Johnston and D. L. Scharfetter “Low fre-

PATT diodes.

rate determined by the external circuit; the low-frequency cycle repeats, beginning again with a growing IMPATT oscillation. The power generating frequency is therefore less than the classical IMPATT frequency.

3) New Frequency and Average Power Scaling Results for High Pulse Power LSA Devices-W. K. Kennedy, Jr. , W . 0. Camp, and L. F. Eastman, Cor- ne11 University.

4) Two-Dimensional Gunn-Domain Dy- namics--M. Shoji, Bell Telephone Laboratories, Inc.

5 ) Noise and Non-Linearity in Diodes- J . B . Gunn, I B M Watson Research Cen- ter.

6 ) Dynamic Scsttering-A New Electro- optic Effect in Nematic Liquid Crystals- G. H. Heilmeier; L . A . Zanoni, and L. A . Barton, R C A Laboratories.

7) Efficient Optical Parametric Oscillation Using Doubly and Singly Resonant Cavi- ties-J. E. Bjorkholm, Bell Telephone Laboratories, Inc.

8) Optical Heterodyne Detection at 10.6 pm of the Beat Frequency Between a Tunable Pbo. ssSno.12Te Diode Laser and a COS Gas Laser-E. D. Hink ley , T. C. Harman, and C. Freed, M. I.T. Lincoln Laboratory.

JOINT SESSION I- MICROWAVE DEVICES Chairman: A. L. McWhorter, M.I.T. Lin-

coln Laboratory Organizer: J. A. Copeland, Bell Telephone

Laboratories, Inc. 1) Efficient Three-Octave Tunable Ava-

lanche Diode Oscillations Due to the Interaction of Quasi-Static and Transit- Time Negative Resistances-C. P. Snapp and B . Hoefinger, Cornell Uni- versity.

2) Techniques for Improving the Electronic Frequency Deviation of an IMPATT Oscillator-C. B. Swan, Bell Telephone Laboratories, Inc.

3) High Resolution Multiplication and Current Fluctuation Measurements on Uniform Avalanche Diodes-I. M. Naqvi, C. A. Lee, and G. C. Dalman, Cornell University.

4) Frequency Modulation of Millimeter- Wave IMPATT Diode Oscillators and Related Harmonic Generation Effects- T. P. Lee and R. D. Standley, Bell Tele- phone Laboratories, Inc.

IMPATT diode oscillators has resulted in Recent research on CW millimeter-wave

significant improvements in terms of oscil- lator tunability as compared to the oscillator reported previously. By mounting the diodes in thick resonant iris we have obtained 8 percent bandwidths (3 dB), with bias cur- rent tuning in the 50 to 60 GHz range. The maximum CW output power was in excess of