Study of hot electron effect in sub-micron semiconductor devices.

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The performance of a submicron semiconductor device is strongly affected by the dynamical properties of hot electrons in such a short time scale as a pico second. In a compound semiconductor device, the electron-polar optical phonon interaction predominates the scattering phenomena. In this project, we have studied the quantum size effect on the interaction of hot electrons with ionized impurities and the polar optical phonons in hetero-structures and/or superlattices.We studied numerically the lattice dynamics of hetero-structures and/or superlattices and found that the layered structure does have a strong influence on the optical modes, which are localized within the layers, while the acoustical mode suffers only a slight modification. We proposed a formula for the interaction of electron-localized optical phonons.According to the results mentioned above, the well width dependence of the electron-phonon interaction was studied, and it was shown that the narrower the quantum well is, the longer becomes the relaxation time and the smaller is the binding energy of polarons. The interaction in 2-dimensional system is shown to become more of the short range nature in comparison with the 3-dimensional one.The photo-luminescence spectra of double quantum well superlattice made of GaAs/AlGaAs system was studied. The sample was subjected to the electric field applied parallel to the hetero-interface at cryogenic temperatures. By investigating the variation of the spectra as a function of the electric field as well as the electron temperature, the real space transfer or the inter-sub-band transition via the electron-impurity or the electron-phonon interaction was confirmed for the first time.