CMOS luminescence lifetime sensor for white LED multi-spectral characterization

Time constants and luminescence lifetimes of an InGaN-based white LED at different wavelengths are characterized by a novel multi-cycle charge modulation based CMOS image sensor chip. To enable high sensitivity, we propose parasitic insensitive multi-cycle charge modulation scheme for low-light lifetime extraction. The designed in-pixel CTIA-based structure is able to capture the weak luminescence-induced voltage signal by accumulating photon-generated charges in 25 discrete gated time windows within 10ms, in which each time window has 10us pulse width. A pinned photodiode on chip with 1.04pA dark current is utilized for luminescence detection. The proposed circuitry can achieve 2.1mV/(nW/cm²) responsivity and 4.38nW/cm² resolution at 630nm wavelength for intensity measurement and 45ns resolution for lifetime measurement.