Structure-performance relationships in terahertz quantum cascade detectors

Quantum cascade detectors (QCDs) are promising devices for mid-infrared and terahertz detection, offering fast response, high spectral selectivity, and operation without external bias. This work presents a theoretical comparison of vertical and diagonal QCD configurations based on GaAs/AlGaAs heterostructures. The electronic subband structure is obtained using self-consistent Schrödinger–Poisson calculations, while carrier transport is modeled by including all relevant intersubband scattering mechanisms. Dark current induced Johnson-Nyquist noise is incorporated by evaluating the near zero-bias resistance-area product ( R₀A ) from the conductances of all inter-period transitions. The results show that both configurations exhibit comparable noise levels, while the diagonal configuration achieves, at 10 \,K , a specific detectivity approximately 1.4 × higher than the vertical one owing to its higher responsivity. It also exhibits greater robustness against growth-induced layer-thickness fluctuations. Since the diagonal geometry is evaluated without exhaustive parameter optimization, this 1.4 × improvement should be interpreted as a result for the investigated parameter range rather than as the maximum achievable performance . The responsivity is found to increase with thinner extraction barriers, while R₀A is primarily governed by the inter-period barrier thickness. These findings provide design guidelines for achieving robust, high performance QCDs and highlight the intrinsic advantages of diagonal architectures.