Nanosciences and Nanotechnology

Biography

Biography: Sudip Chatterjee

Abstract

The most extensively studied SL is the one consisting of alternate layers of GaAs and Ga1-xAlxAs, owing to its fabrication. The GaAs layers form the quantum wells and the Ga1-xAlxAs layers form the potential barriers. We wish to note that, the afore mentioned SLS have been proposed with the assumption that the interfaces between the layers are sharply defined with zero thicknesses so as to be devoid of any interface effects. As the potential form changes from a well (barrier) to a barrier (well), an intermediate potential region exists for the electrons. Thus the influence of the finite thickness of the interface on the carrier dispersion law becomes very important since, the carrier energy spectrum governs all the transport properties. In this paper, we shall investigate the DMR for the most interesting case which occurs in QDSLs of graded interfaces and compare the same with that of the constituent materials by formulating the respective one dimensional electron dispersion laws. The Einstein relation occupies a singular position in the whole field of nanotechnology. The diffusion constant (A quantity very useful for device analysis but whose exact experimental determination is rather difficult) can be derived from this relation if one knows experimental values of the mobility. In addition, it is more accurate than any of the individual relations for the diffusivity or the mobility, which are two widely used quantities in carrier transport of nano devices. It is well known from the fundamental works of Landsberg that the Einstein relation in degenerate materials is essentially determined by the energy band structures. It has, therefore, different values in different materials and varies with electron concentration, with the magnitude of the reciprocal quantizing magnetic field under magnetic quantization and with the quantizing electric field as in inversion layers having various carrier energy spectra.

Some of the significant features which have immersed from the studies are a) the ratio increases monotonically with electron concentration in bulk semiconductors: b) The nature of the variations is significantly affected by the band non parabolicity: c) The ratio increases with the magnitude of the quantizing electric field in inversion layers : d) The ratio oscillates with the inverse quantizing magnetic field under magnetic quantization due to the SdH effect : e) The ratio exhibits composite oscillations in quantum confined structures having different dispersion relations. The above characteristics are considered as theoretical predictions and no experimental results are available, to the knowledge of the authors in support of the prediction of materials having degenerate electron concentration. The lack of experimental results emanates from the difficulty of the measurement of the diffusion constant D for degenerate materials.

Key words: SLS, QDSL, DMR.