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Register a new userDiluted magnetic semiconductor heterostructure AlSb/InAs/ZnMnTe with giant Zeeman effect for two dimensional electrons in InAs
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A new approach to the growth of diluted magnetic semiconductors with two dimensional electron gas in InAs quantum well has been developed. The method is based on molecular-beam epitaxy of coherent hybrid AlSb/InAs/(Zn,Mn)Te heterostructures with a III-V/II-VI interface inside. The giant Zeeman splitting of the InAs conduction band caused by exchange interaction with Mn2+ ions has been proved by measuring the microwave radiation induced spin polarized electric currents.
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We have observed that the tunneling magnetoconductance between two-dimensional (2D) electron gases formed at nominally identical InAs-AlSb interfaces most often exhibits two sets of Shubnikov-de Haas oscillations with almost the same frequency. This result is explained quantitatively with a model of the conductance in which the 2D gases have different densities and can tunnel between Landau levels with different quantum indices. When the epitaxial growth conditions of the interfaces are optimized, the zero-bias magnetoconductance shows a single set of oscillations, thus proving that the asymmetry between the two electron gases can be eliminated.
The quantum efficiency of an electroluminescent intersubband emitter based on InAs/AlSb has been measured as a function of the magnetic field up to 20T. Two series of oscillations periodic in 1/B are observed, corresponding to the elastic and inelastic scattering of electrons of the upper state of the radiative transitions. Experimental results are accurately reproduced by a calculation of the excited state lifetime as a function of the applied magnetic field. The interpretation of these data gives an exact measure of the relative weight of the scattering mechanisms and allows the extraction of material parameters such as the energy dependent electron effective mass and the optical phonon energy.
We examine the possibility of intrinsic interface states bound to the plane of In-Sb chemical bonds at InAs/AlSb interfaces. Careful parameterization of the bulk materials in the frame of the extended basis spds^* tight-binding model and recent progress in predictions of band offsets severely limit the span of tight-binding parameters describing this system. We find that a heavy-hole like interface state bound to the plane of In-Sb bonds exists for a large range of values of the InSb/InAs band offset.
We present piezoresistance measurements in modulation doped AlAs quantum wells where the two-dimensional electron system occupies two conduction band valleys with elliptical Fermi contours. Our data demonstrate that, at low temperatures, the strain gauge factor (the fractional change in resistance divided by the samples fractional length change) in this system exceeds 10,000. Moreover, in the presence of a moderate magnetic field perpendicular to the plane of the two-dimensional system, gauge factors up to 56,000 can be achieved. The piezoresistance data can be explained qualitatively by a simple model that takes into account intervalley charge transfer.
We have realized an AlAs two-dimensional electron system in which electrons occupy conduction-band valleys with different Fermi contours and effective masses. In the quantum Hall regime, we observe both resistivity spikes and persistent gaps at crossings between the Landau levels originating from these two valleys. From the positions of the spikes in tilted magnetic field and measurements of the energy gaps away from the crossings, we find that, after occupation of the minority valley, the spin susceptibility drops rapidly, and the electrons possess a {it single} interaction-enhanced g-factor, despite the dissimilarity of the two occupied valleys.
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