Influence of Quantum Confinement on the Carrier Contribution to the Elastic Constants in Nonlinear Optical and Optoelectronic Materials: Simplified Theory and Suggestion for Experimental Determination: Part – I
K.P. Ghatak, S. Bhattacharya, S. Singha Roy and L.J. Singh
An attempt is made in the first part of this paper to study the carrier contribution to elastic constants in quantum wells (QWs) and quantum well wires (QWWs) of nonlinear optical compounds on basis of a newly formulated electron energy spectrum taking into account the combined influences of the anisotropies in the effective electron mass, the spin-orbit splitting and the presence of crystal field splitting respectively. The corresponding results for quantum confined III-V, ternary and quaternary types of optoelectronic materials form a special case of our generalized analysis. The carrier contribution to the elastic constants has also been studied for QWs and QWWs of II-VI and IV-VI compounds. It has been found, taking QWs and QWWs of CdGeAs2, InAs, Hg1-xCdxTe, In1-xGaxAsyP1-y lattice matched to InP, CdS and PbSe as examples for numerical computations that the second and third order elastic constants increase with increasing carrier degeneracy 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 said contribution in QWs and QWWs having arbitrary dispersion laws has also been suggested and the present simplified analysis is in agreement with the suggested relationship. The well-known results for wide-gap materials having nondegenerate electron concentration have also been obtained as special cases of our generalized theory under certain limiting conditions.