The Einstein relation in nanostructured materials: simplified theory and suggestion for experimental determination |
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Authors: | L J Singh S Choudhury S Singha Roy K P Ghatak |
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Affiliation: | (1) Department of Electronics and Communication Engineering, Sikkim Manipal Institute of Technology, 737132 Majhitar, Rangpo, East Sikkim, India;(2) Department of Electronic Science, The University of Calcutta, 92 Acharya Prafulla Chandra Road, 700009 Kolkata, India |
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Abstract: | An attempt is made to study the Einstein relation for the diffusivity–mobility ratio (DMR) in quantum wells (QWs) and quantum well wires (QWWs) of tetragonal compounds on the basis of a newly formulated electron energy spectrum taking into account the combined influences of the anisotropies in effective electron mass, the spin–orbit splitting, and the presence of crystal field splitting, respectively. The results for quantum-confined III–V compounds form a special case of our generalized analysis. The DMR has also been studied for QWs and QWWs of II–VI and IV–VI materials. Taking QWs and QWWs of CdGeAs2, InAs, CdS and PbSe as examples, it was found that the DMR increases with increasing carrier statistics and decreasing film thickness respectively in various oscillatory manners emphasizing the influence of dimensional quantizations and the energy band constants in different cases. An experimental method of determining the DMR in nanostructures with arbitrary dispersion laws has also been suggested and the present simplified analysis is in agreement with the suggested relationship. The well-known results for nanostructures with parabolic energy bands have also been obtained as special cases from this generalized analysis under certain limiting conditions. |
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Keywords: | Einstein relation Nanostructured materials Quantum wells Quantum well wires |
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