PHOTOCONDUCTIVITY OF ERBIUM-DOPED GERMANIUM

We have applied the technique of PhotoThermal Ionization Spectroscopy (PTIS) to the study of an erbium-doped p-Ge epitaxial layer, grown by MBE on an undoped n-type germanium substrate. The Er-doped Ge layer shows continuum photoconductivity response in the far-infrared region extending from 70 cm-1 to 900 cm-1. This type of epitaxial Er-doped Ge layers is a potentially attractive system for photoconductivity detectors of far-infrared radiation. Below 900 cm-1 three acceptor-like charged states can be distinguished with ionization energies of 9, 26.6 and greater-than-or-equal-to 50 meV. Additionally, a study of the photoconductive response of the same sample for radiation from 1000 cm-1 to 10000 cm-1, i.e., for radiation energies well inside the forbidden gap to energies above it, shows a wealth of levels, some of which have previously been associated with erbium.