Marcio Peron Franco de Godoy

Anomalous photoresponse offers promising avenues for advanced applications like on-chip photonics, information processing, all-optical encryption, and advanced photodetectors. This work explores negative photoconductivity (NPC) in CdZnO thin films, studying its dependence on photoexcitation intensity for a wide wavelength range (365-850 nm), including exposure to controlled atmospheres. The NPC, below the optical bandgap, exhibited a linear increase as the photon flux increased, while its correlation with dark conductivity is associated with oxidizing atmospheres. Positive persistent photoconductivity (PPC) replaces the NPC after the illumination interruption. This positive PPC was small for subgap excitation but strongly enhanced for supragap excitation, correlating linearly with its intensity. The NPC behavior is interpreted by a light-activated recombination center involving subgap photoexcitation of majority carriers from deep defect levels, while PPC was associated with electron–hole pair generation dominating for supragap excitation. These findings elucidate the defect-driven carrier dynamics and highlight potential for wavelength-selective and atmosphere-sensitive optoelectronic devices.