Transverse focusing of spin-polarized photocurrents

Abstract

We measure transverse magnetically focused photocurrent signals in an InSb/InAlSb quantum well device. Using optical spin orientation by modulated circularly polarized light an electron spin dependent signal is observed due to the spin-orbit interaction. Simulations of the focusing signal are performed using a classical billiard ball model which includes both spin precession and a spin dependent electron energy. The simulated data suggests that a signal dependent on the helicity of the incident light is expected for a Rashba parameter α > 0.1 eVÅ and that a splitting of the focusing signal is not expected to be observed in linear polarised photocurrent and purely electrical measurements.

Observation of spin dependent photocoductivity in InSb quantum well nanowires

“…We also can exclude the Zeeman effect as the associated spin splitting at 170 mT is approximately 0.25 meV. We therefore attribute the disappearance of the helicity dependence with temperature to a Rashba mediated spin-dependent transport 7 which is related to electron spin orientation.…”

“…8,9 For B > 2B 0 , skipping orbits (edge states) are formed that suppress back-scattering. In the presence of a SO interaction, the cyclotron radius is dependent on the orientation of the carrier spin 7,10 and consequently so too should the value of B 1 . In analogy to a ferromagnetic metal, a spin polarized current will be produced at B ¼ B 1 due to the asymmetry in the resistivity of the spin dependent current channels, which in the case of a semiconductor nanowire is governed by the strength of the SO interaction and by the dominant mechanism for boundary scattering.…”

“…6 In this letter, we report the electrical detection of spin-polarized charge currents in InSb quantum wires with large spin-orbit coupling using the optical spin orientation technique described in Ref. 7.…”

“…This in turn produces a modulation of the preferential spin orientation due to the selection rules of the photo-excited electrons. 7 Both the longitudinal spin-dependent, V heli (/ r þ À r À at 37 kHz), and spinindependent, V photo (1 kHz), photo responses are detected between contacts 3 and 4 by standard lock-in technique. Note that a change of sign in r will cause a p phase shift in V heli signal and will have no effect on V photo .…”

Efficiency droop in InSb/AlInSb quantum-well light-emitting diodes

“…This system is attractive for realizing mid-infrared optoelectronic components, [12][13][14] both for use in applications such as components for non-dispersive infrared gas sensing, 15 but also as a way of exploiting the quantum effects arising from the very small electron mass. 16,17 Although the factors limiting the efficiency of narrow bandgap LEDs have been studied extensively over the last couple of decades, 18 there have been very few reports and analysis of efficiency droop. For example, Krier 19 and Das and Tobin 20 observed efficiency droop in InAs heterostructure and interband cascade Type IIsuperlattice based LEDs, respectively, but only when the devices were driven with long pulses, suggesting that heating was the origin of the droop.…”