The purpose of this paper is to shed further light on the operating characteristics and limitations of IMPATT diodes, particularly those with Read or modified Read structures. This has been achieved by developing efficient and economical computer Programs which incorporate all of the important material parameters and doping profiles in an exact manner. These computer programs are then employed to study the properties of high-efficiency Si and GaAs structures. Some very interesting properties of these devices and the effects of material parameters and doping profiles on their performance are presented and discussed. This leads to a better understanding of these devices and their limitations. Preliminary calculations have also been carried out on an InP IMPATT diode and the results are presented.

IMPATT device simulation and properties

The saturated electron velocity in GaAs is determined at 100 and 150 °C from a comparison of measured and calculated small‐signal impedance of IMPATT devices. The results are in good agreement with the values obtained by extrapolating Gunn effect theoretical calculations at higher fields, while the values used in previously published IMPATT design work were too high.

Determination of saturated electron velocity in GaAs

A series of p-type IMPATT diodes (p+pn+) have been fabricated from epitaxially grown silicon for operation as oscillators at K a -band frequencies. A maximum CW output power level of 700 mW at 29.6 GHz, a maximum conversion efficiency of 10.9 percent, and a minimum FM noise parameter, M, of 25 dB have been measured on this series of p-type diodes. A diode oscillating in a variable height radial disk cavity was frequency tuned from 27.5 to 40 GHz, covering the entire K a -band, with a 1.4 dB power variation over the tuning range. The minimum CW output power of this tunable oscillator was 360 mW at 6.5 percent efficiency.

Performance of P-type epitaxial silicon millimeter-wave IMPATT diodes

High-efficiency performance of GaAs Schottky-Read IMPATT diodes has been observed at X-band frequencies. The highest efficiency measured was 26.1 percent with 2.5-W continuous-wave (CW) output power at 8.8 GHz for a single-mesa diode while multiple-mesa diodes have delivered more than 7 W at X band. The diodes were fabricated from multiple-layer epitaxial material with gold-plated heat sinks. Details of materials preparation and diode fabrication are presented. Theoretical calculations of diode breakdown voltage and efficiencies have been made as a function of the structural properties of the diodes. Good agreement has been obtained between the experimental microwave oscillator performance and the theoretical calculations.

GaAs Schottky&#8212;Read diodes for x-band operation

A technique for investigating the role of dynamic or effective leakage current in the r.f. performance of an impatt diode is described. The technique involves the design of a device structure and microwave cavity which permits the leakage current to be varied externally by photogeneration of carriers, and is compatible with c.w. operation. Typical results for flat-profile single-drift X-band silicon are a 10% reduction in power and a 10 MHz increase in frequency at a photo/bias-current ration of 0.005.

Leakage current enhancement in impatt oscillators by photoexcitation

The basic principles of IMPATT diodes as microwave devices are reviewed and the current status of these devices concerning power output and efficiency is given. The main purpose of this paper, however, is to discuss the nonlinear properties of these diodes which are useful in the design of amplifiers, oscillators, and other microwave devices. The main results of this paper are obtained from a digital computer analysis where an approximate, but realistic, diode model is employed. A detailed comparison of complementary silicon diodes as well as GaAs diodes concerning power output and efficiency is given. The effects of doping profile, current density, temperature, and material parameters on the performance of these devices have been investigated and are summarized. Saturation effects which limit the efficiency and power output of these devices are described and optimum efficiencies which can be achieved for various doping profiles are given. A comparison between single-sided and double-drift diodes in both silicon and GaAs is also presented.

W.E. Schroeder

Papers

Nonlinear properties of IMPATT devices