Janus-Faced Carrier Localization with Defect States: A Case Study in InGaN-Based Photodetectors

The multifaceted behaviors of defect states in semiconductor photodetectors often preclude a direct correlation between the detection performance and material crystalline quality, posing challenges for researchers in optoelectronic materials and devices. Here, through multidimensional characterization of InGaN-based detectors with varying defect configurations, we elucidate the dualistic effects of the material defects. Both dislocation-related deep-level traps and localized states capture minority carriers, generating additional photoconductive gain and enhancing the responsivity. Notably, under weak light conditions, defect-assisted gain induces an increase in responsivity. However, carrier localization inevitably compromises the response stability, operational thermal range, and dynamic linearity, thereby causing practical limitations. These results will surely contribute to establishing a framework for material and device designs tailored to practical detection requirements; meanwhile, the proposed methodology enables rapid identification of defect-associated photoconductive effects in photodetectors. Moreover, the conclusions also have broad significance beyond InGaN-based photodetectors, offering practical guidelines for optimizing defect states in various semiconductor photodetectors.