Far-Infrared Absorption Spectra of Sb-Doped Ge at Low Temperature

Abstract

The concentration dependence of far-infrared absorption spectra of antimony-doped germanium with 6×10 14 to 7×10 16 cm -3 , has been investigated in the wavelength range of 100 µm to 1 mm. In the excitation spectra, a higher energy line broadens faster with impurity concentration that a lower one, and disappears. In addition, the excitation lines shift slightly their position to lower energies and broaden in the low energy side with increasing concentration. Above 5×10 15 cm -3 , background absorption appears newly as a curve of gradual descent from the ionization limit toward low energies, and increases rapidly with concentration. This absorption spreads over the whole spectral range at 7×10 16 cm -3 , which would be responsible to the bolometric action. A qualitative discussion of the concentration effects is given. For sample having a small thickness (≈100 µm), the doublet structure of the excitation spectra was observed to change by surface treatment.