The theory of direct-current characteristics of rectifiers

It is shown how the image force can be taken into account very simply by making a minor improvement in the current theory of rectification. The equations obtained have been compared with experimental d. c. reverse characteristics of the copper oxide, selenium and germanium rectifiers, assuming in each case, first, that a Mott barrier is present, and, secondly, that a Schottky barrier is present. Agreement is satisfactory, the hypothesis of a Schottky barrier leading to a slightly better fit in all cases. As regards the numerical constants calculated from a fit of the experimental results, satisfactory values can be obtained if a Mott barrier is assumed. If a Schottky barrier is presupposed, the results for the copper oxide and selenium rectifier lead to very low values for the mobilities and high values for the impurity centre densities in the barrier region. This is discussed. The effect of the image force on the current carrier distribution is illustrated, and a general relation between the diffusion and diode theory established.