We use electron spin resonance in the far infrared to probe the Landau-level spin splitting in symmetric and asymmetric InSb quantum wells. The asymmetric wells exhibit a strong deviation in behavior from the symmetric wells at low magnetic fields with apparent g factors far in excess of the bulk g factor of InSb. These asymmetry-induced shifts in the spin resonance depend on Landau-level The study of electron spin phenomena in semiconductor heterostructures has intensified dramatically in recent years. The field, "spintronics" has emerged with the purpose of developing devices combining the charge and spin degrees of freedom. In particular, spin splitting caused by bulk inversion asymmetry and structural inversion asymmetry (SIAoften called Rashba splitting) has attracted much attention. Understanding the spin-orbit interaction caused by SIA, which is predicted to lead to spin splitting even without an applied magnetic field, 1,2 is important for developing spinbased devices. To date, experimental evidence for Rashba splitting in two-dimensional electron systems (2DESs) has been chiefly confined to the observed beating of Shubnikov-de Haas (SdH) oscillations 3,4 that is presumed to arise from different populations of electron spin orientations. This beating has been interpreted in a number of heterostructures [3][4][5][6][7][8][9][10][11][12][13][14][15][16] to deduce the Rashba parameter ␣, which is expected to depend on materials parameters and the electric field. The zero-field spin splitting has also been inferred from Raman-scattering spectra 17 in GaAs and weak anti-localization measurements in InGaAs quantum wells 18 . In this paper, we report on electron spin resonance (ESR) experiments on 2DESs in InSb quantum wells. By observing transitions between states with the same Landau level index but opposite spin orientations, we directly measure the spin splitting as a function of applied magnetic field B. In addition to the B = 0 spin splitting, the Rashba model 1 predicts considerable modification of the Landau-level energy structure at nonzero B for asymmetric heterostructures, which has not been previously confirmed. Because of the large effective g factor and large predicted Rashba effect, 6 the spin splitting in InSb-based 2DESs should occur at far infrared frequencies for B Ͻ 10 T. Our experiments demonstrate that the Rashba effect is relatively strong in InSb quantum wells and that ESR is a powerful technique for studying the Rashba effect.Our samples are InSb single quantum wells of widths 30 and 20 nm with Al 0.09 In 0.91 Sb barrier layers that are ␦ doped with Si. The Si ␦ layers are located either singly on one side of the quantum well (asymmetric samples) or equidistant on both sides of the quantum well (symmetric samples). The ␦-doped layers within the barrier layers are typically located 70 nm from the well center. The barrier layers on the substrate and surface sides of the wells are 3 m and 160 nm thick, respectively. Silicon dopants are placed near the surface to limit surface depletion. ...

Articles you may be interested inHigh electron mobility in InSb epilayers and quantum wells grown with AlSb nucleation on Ge-on-insulator substrates J. Vac. Sci. Technol. B 32, 02C116 (2014); 10.1116/1.4866397 Improved electron mobility in InSb epilayers and quantum wells on off-axis Ge (001) substrates Impact of structural defects upon electron mobility in InSb quantum wellsWe observe a significant increase in InSb quantum-well mobility when remote doping of Al 0.09 In 0.91 Sb barriers is accomplished by three layers, rather than one layer, of Si ␦ doping. At 7 K, the electron mobility in single quantum-well structures grown on GaAs substrates is as high as 280 000 cm 2 /V s with an electron density of 2.33ϫ10 11 cm Ϫ2 . The density of oriented abrupt steps and square-mound features on the sample surface correlates with the electron mobility in the well.

We use transmission spectroscopy to determine the energy gap for the AlxIn1−xSb alloy system in the Al concentration range from 0% to 25% from cryogenic to room temperature. The samples are epitaxial layers grown by molecular beam epitaxy on GaAs substrates. Our room temperature results are compared to those from two earlier studies. In our Al concentration range, we find a linear change of energy gap with alloy lattice constant.

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We report the observation of interband exciton transitions in InSb/Al x In 1Ϫx Sb multi-quantum-well samples. The exciton peaks are identified with the use of a simple quantum well model. The strain present in the InSb wells alters the spectrum significantly from that for unstrained III-V materials and makes it possible to use the exciton spectrum in determining the band offset.