Infrared Illumination-Induced Responsivity Enhancement in Photoelectric Tunable-Step Terahertz Detectors

Quantum phenomena in 2D electron gases (2DEGs) provide new opportunities for high-responsivity far-infrared detection. A prime example are photoelectric tuneable-step (PETS) terahertz detectors, which use the in-plane photoelectric effect as a sensitive photonic detection mechanism. Here, we show that the terahertz sensitivity of this quantum photodetection mechanism can be dynamically tuned using infrared illumination. We leverage the persistent photoconductivity effect in AlGaAs/GaAs-based heterostructures to tune the device performance by adjusting the electron density and mobility in the channel. Our approach enables optimization of the responsivity for different operating modes and dynamic control over the output impedance of PETS terahertz detectors of approximately one order of magnitude. We provide an explanation for the underlying physics, which advances the understanding of quantum photodetection phenomena in 2DEGs. Our findings pave the way to in-situ tunable optoelectronics combining concepts from the infrared and terahertz spectral regions.