Time constant of the far-IR response of a quantum Hall device

Abstract

Abstract. The characteristic time of far IR response of quantum Hall effect detector in GaA/AlGaAs has been investigated versus the magnetic field. The response time is shown to increase dramatically with the field due to the spatial separation of photoexcited electrons and holes captured by localized states formed by the disordered potential.

Magnetic field dependence of the photoresponse time of GaAs/AlGaAs quantum Hall effect device

“…Though in this case the QHE plateau is less developed and there is only one pronounced peak of the photoresponse (on the right-hand side of the plateau), the response time dependence on the magnetic field exhibits a two-peak structure with the minimum at the plateau center. In strong magnetic fields the response time increases exponentially with the field [5,11] in accordance with the relation (1). From the increase in the response time at ν = 2 (right peak) if compared with that at ν = 4 (figures 1, 2) one can determine the characteristic magnetic fields B * and obtain the following data for Y: These values are two times less than those obtained for the sample with higher mobility [11] in accordance with the proposed mechanism of the photoresponse of QHE detector [5].…”

“…In strong magnetic fields the response time increases exponentially with the field [5,11] in accordance with the relation (1). From the increase in the response time at ν = 2 (right peak) if compared with that at ν = 4 (figures 1, 2) one can determine the characteristic magnetic fields B * and obtain the following data for Y: These values are two times less than those obtained for the sample with higher mobility [11] in accordance with the proposed mechanism of the photoresponse of QHE detector [5].…”

“…Due to a small overlapping between the electron and hole wavefunctions in high magnetic fields, the lifetime τ increases exponentially with the magnetic field [5,11],…”

“…where the magnetic field B * is related to the characteristic distance Y as Y = 2(hc/eB * ) 1/2 [11]. Here h is the Planck constant, c is the light velocity and e is the electron charge.…”

“…Here h is the Planck constant, c is the light velocity and e is the electron charge. Indeed, the photoresponse time constant has been shown to increase exponentially with the magnetic field by tuning the photoresponse peak to higher magnetic fields by increasing 2D electron concentration using the persistent photoconductivity effect [11]. At the same time, at a constant 2D electron gas concentration a characteristic minimum of τ was observed in the center of the QHE plateau corresponding to the filling factor ν = 2 [5].…”