Existence of a phonon bottleneck for excitons in quantum dots

A phonon bottleneck is manifested for correlated electron/hole (exciton) states in self-organized InₓGa_1-xAs/GaAs quantum dots (QD's) with a flat, truncated shape. Suppressed relaxation and hot luminescence from excited states in the low-density regime are demonstrated. The long low-temperature relaxation time of ~7.7 ns, being ~15 times the radiative lifetime, is attributed to a quenched polar exciton-LO-phonon coupling in truncated QD's based on eight-band k·p model calculations.