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Behavior of some metallic impurities in germanium : investigation by transient spectroscopy methods - Deep Level Transient Spectroscopy-Minority Carrier Transient Spectroscopy - Laplace Deep Level Transient Spectroscopy

Abstract : The present work is an attempt to re-examine the electronic properties of Fe, Ni Cr and Au in Ge which have been already studied by conventional DLTS (Deep Level Transient Spectroscopy). A general picture, that emerged, is that transition metals in Ge predominantly form multiple-acceptor centres, introducing several deep levels in the band gap, which according to a simple valence bond model is in agreement with a preferential occurrence of the impurities on substitutional sites. However, some questions remained open such as the role of hydrogen as a natural contaminant in the broadening of the DLTS spectra. Our contribution is based on the use of a more powerfull approach called Laplace DLTS in the sense that it allows a better resolution of the signal. We present extensive DLTS, MCTS and Laplace DLTS results to investigate the electronic properties of the multi-acceptor states, induced by mentioned four transition metals. Among the studied parameters we may cite the barrier for carrier capture, the true majority carrier capture cross section directly measured by the variable pulse length method, the Poole-Frenkel effect related to the assignment of the charge states - all these parameters are important to locate the level positions in the band gap. We confirm in the present work most of the results obatained in the past, adding some insight into the role of hydrogen in the formation of new complexes and in this respect a parallel is made with silicon. In case of Au new levels attributed to conjectural Au-Hn and Au-Sb complexes are observed. In addition development of both majority and minority carriers in MCTS analysis still is under consideration. For the Fe case, the small difference in energy of its two levels raises the question as to the possibility of negative-U character. These mentioned points should be treated more thoroughly in a future work.
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Yana Gurimskaya. Behavior of some metallic impurities in germanium : investigation by transient spectroscopy methods - Deep Level Transient Spectroscopy-Minority Carrier Transient Spectroscopy - Laplace Deep Level Transient Spectroscopy. Electronics. Université de Strasbourg, 2012. English. ⟨NNT : 2012STRAD008⟩. ⟨tel-00734375⟩

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