Negative differential conductance in cleaved edge overgrown surface superlattices AIP Conf. Proc. 772, 900 (2005); 10.1063/1.1994398Negative high-frequency differential conductivity in semiconductor superlatticesWe analyze the transport properties of a semiconductor superlattice in the presence of a biharmonic electric field. The modification of current-voltage characteristics induced by the biharmonic radiation is obtained. The conditions for absolute negative conductivity and for the spontaneous generation of a significant static electric field are determined. We also show that a simple harmonic field can experience nonlinear amplification even when the differential superlattice dc conductivity is positive, and we determine the corresponding range of parameters.

The nonlinear oscillations of field and current in semiconductor superlattices excited by terahertz laser radiation are studied within a self-consistent multifrequency internal field approach. We show that the oscillatory character of the nonlinear susceptibilities and dissipative and parametric instabilities in superlattices leads to multivaluedness and hysteresis of their spectral harmonics as functions of the external field amplitude. The key mechanisms of such spectral behavior are the spontaneous generation of a static field and parametric creation and amplification of the external field harmonics and subharmonics. It is shown that the field inside the superlattice cannot be understood in terms of a single frequency, especially for superlattices having high electron concentration.

The phenomenon of transparency in two-dimensional and three-dimensional superlattices is analyzed on the basis of the Boltzmann equation with a collision term encompassing three distinct scattering mechanisms (elastic, inelastic and electron-electron) in terms of three corresponding distinct relaxation times. On this basis, we show that electron heating in the plane perpendicular to the current direction drastically changes the conditions for the occurrence of self-induced transparency in the superlattice. In particular, it leads to an additional modulation of the current amplitudes excited by an applied biharmonic electric field with harmonic components polarized in orthogonal directions. Furthermore, we show that self-induced transparency and dynamic localization are different phenomena with different physical origins, displaced in time from each other, and, in general, they arise at different electric fields. Typeset using REVT E X 1 1

The objectives of this investigation are structural and physical characteristics of the n-Sii_Ge/n(p)-Si heterojunction under strong elastic deformation of Si1_Ge layers which gives rise to misfit dislocations in the heteroboundary region; the factors playing the main role in formation of the band structure of the system; the use of transmission electron microscopy and optical methods for determination of the phenomena connected with misfit dislocations in the grown epitaxial structure; the electrical characteristics of diode structures and the process of electron-hole recombination via dislocation states in a heterojunction.

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