SCAPS-1D Simulation Study on Effect of Absorption Layer Thickness on the Performance of p-CuI/n-InSe Near-Infrared Photodetectors

Abstract

Photodetectors based on van der Waals semiconductors are promising candidates for next-generation optoelectronics due to their tunable bandgaps and environmental stability. In this work, the performance of a p-CuI/n-InSe heterostructure photodetector was systematically investigated using SCAPS-1D simulations. The effect of varying the InSe absorber thickness (0.40–0.60 μm) was analyzed in terms of dark current, quantum efficiency (QE), spectral responsivity (Rλ), and specific detectivity (D*). The results reveal that increasing the InSe thickness suppresses dark current, improves carrier collection, and enhances sensitivity in the near-infrared (NIR) region. A peak responsivity of ~0.62 A/W was achieved at 864 nm, corresponding to the bandgap of InSe (~1.25 eV). Better noise performance was confirmed by the QE exceeding 96% for thicker layers and the rise in D* values over the 300–1100 nm spectral region. These results demonstrate how important it is to optimize absorber thickness while creating reliable, lead-free NIR photodetectors.