Engineering Slow-Carrier Interfacial Recombination Enables Tailored Spectral Response

Photocarrier surface recombination is a critical process in optoelectronics. Here, we report that when photocarriers traverse generic semiconductor surfaces or certain carrier-transport layers, slower carriers-arising from weaker electric-field-driven drift-are more likely to be trapped by defect states and subsequently recombine. This process can be engineered to unlock emergent optoelectronic functionalities. Proof-of-concept experiments are proposed in which a wide space-charge region (tens of µm in width) is created in a semiconductor, and photocarriers are generated at locations with distinct electric potentials to observe their surface collection rates. The transport of photocarriers is intentionally impeded to distinguish their dynamics. We examine a variety of interfaces, including direct electrical contacts, surfaces with intentionally introduced defects, and defective organic contacts. It is observed that carriers generated in regions of low electric potential preferentially recombine, offering the possibility for tailored spectral response in semiconductor heterointerfaces. By manipulating slow-carrier recombination, a silicon (Si) narrowband photodetector with ∼100 nm full width at half maximum (FWHM) is demonstrated. Semiconductor surfaces/interfaces are natural filters that capture weak-drift slow carriers.