Simple theoretical analysis of the thermoelectric power under strong magnetic quantization in superlattices of non-parabolic semiconductors with graded interfaces

An attempt is made in this paper to present a simple theoretical analysis of the thermoelectric power under strong magnetic quantization (TPM) in III-V, II-VI, PbTe/PbSnTe, strained layer and HgTe/CdTe superlattices (SLs) with graded interfaces and compare the same with that of the constituent materials by formulating the respective magneto dispersion laws, which in turn control all the transport properties through Bolzmann transport equation. It has been observed, taking GaAs/Ga1-x Al x As, CdS/CdTe, PbTe/PbSnTe, InAs/GaSb and HgTe/CdTe with graded interfaces as examples, that the TPM exhibits oscillatory dependence with the inverse quantizing magnetic field due to the SdH and allied SL effects and increases with increasing inverse electron concentration in an oscillatory manner in all the cases. The nature of oscillation is totally band structure dependent and the width of the finite interface enhances the numerical values of the TPM for all the aforementioned SLs. The numerical values of the TPM in graded SLs are greater than that of the constituent materials. The theoretical results are in quantitative agreement with the experimental results as given elsewhere. The well-known expressions for the bulk specimens of wide-gap materials can also be obtained as special cases of our generalized analysis under certain limiting conditions. In addition, we have suggested the experimental methods of determining the Einstein relation for diffusivity-mobility ratio, the Debye screening length and carrier contribution to the elastic constants, respectively, for materials having arbitrary dispersion laws