Interband Electro-Optical Properties of Germanium. I. Electroabsorption

Abstract

In this and in the following paper, we report on the effect of an electric field on interband optical transitions in germanium. We have measured the electroabsorption effect on the direct edge of germanium at three different temperatures: 14, 83, and 300\ifmmode^\circ\else\textdegree\fi{}K. The amplitude of the signal increases fivefold from the highest to the lowest temperature. Analysis of the temperature and electric-field dependence of data show that there is very little relationship between the data and the predictions of one-electron band theory (Franz-Keldysh effect). It will be shown that the Coulomb interaction (the exciton and its continuum of states) is probably responsible for most of the observed behavior at both low and high temperatures.