A study of thermal effects in the reverse characteristics of germanium point contact diodes

Previous work on the reverse current-voltage characteristics of Ge point contact diodes has shown the presence of a voltage maximum ("turnover"). The present investigation is an attempt to explain the fact that the power dissipated at this voltage maximum decreases with increasing ambient temperature. Using diodes which were given rigorous tests to ensure stability of operation, accurate reverse characteristics were obtained at carefully controlled ambient temperatures. On the basis of a model involving surface leakage currents as well as the main bulk flow, a current characteristic involving two activation energies was proposed. It was shown that this model was capable of giving the observed behavior of the turnover power. Using parameters obtained from the static constant-voltage plots, the theoretical dependence of the turnover power on ambient temperature was obtained and was very closely the same form as that found experimentally by Benzer over a very wide range of temperature. By adjusting one parameter (the dissipation constant) excellent agreement was obtained between the theoretical turnover power and that measured in the present experiments. A series of pulse measurements established the fact that the thermal relaxation time of the diode was less than 1 μsec. The experimental and theoretical study presented here shows that a completely consistent model for the turnover phenomenon can be constructed in terms of a reverse current composed of two components with different activation energies; physically there is evidence that these components correspond to bulk and surface current flow.Science, Faculty ofPhysics and Astronomy, Department ofGraduat