Existence of symmetry-broken excited states in single and ensemble quantum ring structures

Power-dependent time-integrated/time-resolved photoluminescence (PL) measurements of the quantum ring (QR) structures were performed under 4 K. As excitation power is increased, the exciton and biexciton states were confirmed by linearly and superlinearly increasing power factors, respectively. Notably, the power-dependent blue shift showed fine structure splitting owing to the diverse sizes of the excited states. These different excited states could be distinguished by measuring the power-dependent decay times. Asymmetric electron–hole exchange interactions, attributed to the different sizes of energy states and different oscillator strengths between the ground and excited exciton states, were analyzed using time-resolved PL techniques. The various excited states were resolved based on their exponential decay rates.