Reverse Characteristics of High Inverse Voltage Point Contact Germanium Rectifiers

Abstract

A theory of the reverse characteristic of high inverse voltage germanium rectifiers is developed, which takes account of the radial symmetry of the point contact and the presence of positive holes in the ``inversion region'' of the semiconductor. The field at the metal is found to consist of three components. The first component varies inversely with the radius of the contact and directly with the applied voltage for larger voltages. The second component is produced by the impurity centers and varies approximately as the cube root of the voltage. The third component is produced by the positive holes in the inversion region and is approximately constant. This last component lowers the effective barrier height for rectifiers made of very pure material. The first is the more important of the variable components and is responsible for increases in current resulting from image force and tunnel effect at high voltages. In the former case the logarithm of the current varies as V^½ and in the latter as V² approximately. Current‐voltage curves of the predicted forms have been found experimentally using short rectangular pulses varying in length from 2 to 10 μsec to minimize thermal effects. Where possible, barrier heights are determined by measurements over a range of temperatures and detailed numerical comparisons of theoretical and experimental data are made. The two sets of data are in remarkably good agreement thus implying that the theoretical picture is essentially correct.