FAR-INFRARED ABSORPTION-SPECTRA OF IMPURITY BAND IN N-TYPE GERMANIUM

Far-infrared absorption spectra in As- or Sb-doped germanium in the intermediate impurity concentration range have been investigated at 1.5 K. A steep rising of the absorption toward higher energies is found in the spectra, and their energies are closely connected with the thermal activation energies ε2's which are determined by simultaneous measurements of the D.C. resistivity. The concentration effect and [111]-uniaxial compressive stress effect have shown that the absorption is attributed to the electronic transition from the impurity ground states to the upper Hubbard band. The evidence of the variable-range hopping is obtained from the shape of the tail of the spectra. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.