Optical Properties of Heavily Doped Compensated Germanium

Abstract

Measurements of the optical properties of a compensated heavily doped sample of germanium are reported. Although the sample contained about ${10}^{20}$ gallium atoms/cc and ${10}^{20}$ arsenic atoms/cc, the compensation was such that the absorption coefficient could be measured from a minimum value of 7 ${\mathrm{cm}}^{-1\mathrm{}}$ to a maximum at about ${10}^4$ ${\mathrm{cm}}^{-1\mathrm{}}$. The major observation was that of an exponential tail beginning at about 0.78 eV which was not strongly dependent on the carrier concentration for densities between 2×${10}^{17}$/${\mathrm{cm}}^3$ and ${10}^{19}$/${\mathrm{cm}}^3$.