Observation of an Atomlike Energy Spectrum with Large g Values by Tunneling Spectroscopy

We report the observation of localized energy levels in the forbidden gap of PbTe by tunneling spectroscopy in PbTe-Al₂{O}₃$-metal junctions. This study reveals the existence of deep centers in the neighborhood of the PbTe surface, in which the energies of major levels are approximately inversely proportional to ${n}²$ ($nan integer, ≥3). Many of the levels show enormously largeg$ values (up to 18), which seem to suggest a mixing of these localized states with the bands in PbTe.