Temperature and bias voltage control of helicity-dependent photocurrent in PbTe/PbEuTe quantum wells

We present a systematic investigation of helicity-dependent photocurrent (HDPC) in epitaxial PbTe quantum wells (QWs), revealing a striking transition in the dominant mechanism upon Pb doping. While the undoped QW exhibits predominantly the circular photon drag effect, Pb doping triggers a crossover to the circular photogalvanic effect. This transition is mainly attributed to the doping-enhanced spin–orbit coupling (SOC) strengths. Crucially, the absence of HDPC when the photocurrent-collecting electrodes are aligned within the laser incidence plane provides rigorous confirmation of the system's C3v symmetry, excluding extrinsic symmetry-breaking artifacts. Quantitative analysis of the Rashba-induced effective electric field (αe) reveals distinct temperature dependence: the Pb-doped QW exhibits a positive correlation between the SOC strength and temperature, whereas the undoped QW shows a negative trend. Furthermore, bias-dependent modulation demonstrates superior HDPC tunability in the undoped QW, facilitated by its higher photocarrier concentrations. These findings establish PbTe QWs as a promising platform for opto-spintronic device design.