Invited paper. Avalanche diode oscillators. I. Basic concepts

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Abstract
This is the first of a series of three papers in which the basic physics of IMPATT diodes, their applications and limitations, and their prospects for the future will be discussed. This, the first instalment, concentrates on the underlying physical phenomena and the basic theory of the device. The fundamental semiconductor properties are reviewed, followed by a basic account of the avalanche and drift processes. This leads on to a description of the Read diode and an analysis of the device baaed on the sharp pulse approximation, whore approximate large signal limits are derived. The treatment of the device theory is then extended to give a realistic feel for the impact of various material parameters on device operation. The technique in to examine EACH material parameter as a perturbation on the sharp pulse approximation, and in this MANNER the effects of the following parameters arc examined : (1) The relationship between the r.f. voltage and the electric field distribution throughout the cycle, including the effects of space charge during the transit time. (2) Deviations from the sharp pulse to a distributed injection—effectively accounting for finite avalanche zone width. (3) The effect of depletion layer width modulation on device operation to introduce generalized form of the Ramo-Shockley theorem. (4) The effect of real velocity-field characteristics on the basic device charac-teristics. A number of the associated issues also covered including back bias and an elementary account of the impact of unequal ionization rates. This paper, which covers the phenomena pertinent to the avalanche diode, forms the foundation for the discussions of the actual device in the succeeding instalments.

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