ABSORPTION OF 54-78 GHZ ELECTROMAGNETIC-RADIATION BY LIGHTLY DOPED P-TYPE GERMANIUM

An experimental investigation was made of the dependence of the absorption of 54-78 GHz radiation by p-type germanium with a resistivity 48-50 Omega . cm on the concentration of electron-hole pairs. The pair concentration was increased by passing an injection current through n(+)-p and p(+)-p junctions and by increasing the temperature of a germanium crystal. The dependence of the absorption on the injection current and on temperature observed on increase in the frequency from 54 to 78 GHz was first anomalous and then changed to normal, followed by anomalous, and normal again. The normal dependence was characterized by an increase and the anomalous by a reduction in the absorption of radiation on increase in the pair concentration. The anomalous dependence was attributed to a change in the strength of the interaction of radiation with the surface potential barrier on increase in the pair concentration in the bulk of germanium.