Experiments on the Interface Between Germanium and an Electrolyte

This paper reports studies of germanium electrodes in contact with aqueous electrolytes. Measurements have been made of electrode po- 130 T H E B E L L SYSTEM TECHNICAL J O U R N A L , J A N U A R Y 1955 tentials for germanium electrodes in contact with aqueous solutions of potassium hydroxide, potassium chloride and hydrochloric acid. Measurements were made as a function of anode or cathode current and also of light intensity. In one series of experiments with n-type germanium simultaneous measurements were made of changes in the density of the minority carriers, i.e., holes. The measured half cell potentials may be understood in terms of the following conclusions. At a germanium anode, the primary reaction is with holes in the semiconductor and not with electrons. 1 Because of the long lifetime of minority carriers in high purity germanium, one can establish a steady (quasi-equilibrium) state in which the density of minority carriers may differ by many orders of magnitude in either direction from the equilibrium value. One way in which this may be done is to illuminate the surface. Illumination of the surface creates equal numbers of holes and electrons. The effect upon the density of majority carriers is not very large but the relative change in the density of minority carriers may be considerable. It is found that the effect of light on the electrode potential for a p-type germanium anode is rather small, but that for n-type the effect is large. The electrode potential is found to depend upon the concentration of holes in the way which one would expect from thermodynamics if the holes are taking part as one of the components in the anodic process.