Performance optimization and mechanistic investigation of GaAs/AlGaAs-based quantum cascade detectors with multi-stage coupled structures

Quantum cascade detectors (QCDs) exhibit significant application potential in the infrared to terahertz spectral range due to their intersubband transition properties. However, limitations such as interface scattering and atomic-scale structure instability in traditional cascade structures hinder the improvement of their respond performance. In this study, GaAs/AlGaAs-based QCD samples with a four-well cascade structure (FWCS) and two multi-stage coupled structures (MSCS-1 and MSCS-2) were fabricated using molecular beam epitaxy (MBE). The correlation mechanisms between the atomic-scale structure of heterojunctions and respond performance were systematically analyzed through X-ray diffraction (XRD), synchrotron radiation X-ray absorption spectroscopy (SR-XAS), and band structure simulations. XRD and XAS collectively confirmed that the heterojunction interface bond length consistency in the MBE-grown FWCS and MSCS samples achieved atomic-scale precision, with a material parameter deviation of only 0.8 % from theoretical design. Respond performance experiments and band structure simulations demonstrated that MSCS-1 and MSCS-2 achieved 3-5 orders of magnitude enhancement in dark current density and blackbody-induced response current density compared to FWCS, which attribute the multi-stage coupled structure enhances energy level coupling in the transport region, forming a miniband transport that significantly improves carrier transport efficiency. Specifically, MSCS-2 due to its optimized energy level alignment, exhibited a blackbody-induced response current density of 1.45 × 10⁻⁴ A cm⁻² under a −1 V bias and a reduced activation energy of 102 meV. This study provides critical theoretical support for the band engineering and structural design of high-performance QCDs.