Carrier dynamics in undoped and modulation-doped self-assembled InAs/GaAs quantum rings was comprehensively examined through time-resolved photoluminescence techniques at room temperature. After photoexcitation, the rates of carrier capture and relaxation in the ground state and excited states were equally fast in both the undoped and charged quantum rings. Instead of cascading down through the excited states, the carriers excited in the undoped quantum rings relaxed through the quasicontinuum

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... tates via coupling with acoustical phonons and eventually thermalized to the ground state by emitting longitudinal optical phonons. The dynamics of carrier thermalization was governed by cold carriers in the charged quantum rings. In carrier recombination, the undoped quantum rings had a shorter PL decay time and lower luminescence intensity than the charged quantum rings because radiative recombination was suppressed by defects in the matrix and the absence of cold carriers. carrier capture, relaxation, and recombination in the barriers, wetting layers (WLs), excited states and GSs of undoped and modulation-doped self-assembled InAs/GaAs QRs. We describe the dependence of PL rise and decay times on cold carriers and the defects QRs matrices.