Spectroscopic studies of iron and chromium in germanium

We report on the electronic properties of Fe and Cr in n-type germanium studied using conventional and Laplace Deep Level Transient Spectroscopy techniques (LDLTS). Using Schottky barriers restricts the studies to levels located in the upper half of the band gap. However, by applying external optical excitation to generate minority carriers, the investigation is extended to the lower half of the band gap. Major findings already published by other authors are in several cases confirmed. However, new insight is revealed on the microscopic behavior of these two chemical species such as their interactions with hydrogen giving rise to the generation of complex-related levels in the band gap. For the Fe case, the small difference in energy of its two levels raises the question as to the possibility of negative-U character.