Optical properties of heavily doped compensated germanium

Measurements of the optical properties of a compensated heavily doped sample of germanium are reported. Although the sample contained about 1020 gallium atoms/cc and 1020 arsenic atoms/cc, the compensation was such that the absorption coefficient could be measured from a minimum value of 7 cm-1 to a maximum at about 104 cm-1. 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 2×1017/cm3 and 1019/cm3. © 1962 The American Physical Society.