Influence of transverse confinement on the in-plane photoelectric effect in two-dimensional electron systems

Sensitive terahertz (THz) detectors are essential for all THz applications. The recently unveiled in-plane photoelectric effect is a novel, quantum mechanism enabling terahertz detection with high responsivities in 2D electron gases (2DEGs). Here, we investigate the influence of transverse confinement in 2DEGs on the in-plane photoelectric response by measuring AlGaAs/GaAs-based photoelectric tunable-step THz detectors with symmetric antennas but different shapes of the underlying 2DEG. Despite fully symmetric antennas, the geometric channel asymmetry notably shifts the gate voltage dependence of the photoresponse. Our findings underscore the highly localized nature of the in-plane photoelectric effect as a quantum photodetection mechanism. The results show how tailored shapes of 2DEG channels influence the quantum-mechanical photocurrent arising along the electron channel direction by modifying the number of subbands corresponding to electron motion perpendicular to the channel. Our work shows that quantum effects influence photodetection phenomena not only along the direction of electron flow but also in the transverse, perpendicular direction—even in degenerate 2DEGs and on length scales of several microns. This provides a path to structural engineering of quantum light–matter interactions in 2DEGs.