Emission from discrete levels in self-formed InGaAs/GaAs quantum dots by electric carrier injection: Influence of phonon bottleneck

We studied the excitation-power dependence of photoluminescence (PL) spectra and the current dependence of electroluminescence (EL) spectra of self-formed InGaAs/GaAs quantum dots. We observed five peaks in the PL and EL spectra. From the size dependence of the peak interval and the carrier-density dependence of peak energy and peak intensity, we assigned the peaks to the discrete energy levels in the quantum dots. We simulated the EL spectra with rate equations, taking into account the carrier relaxation between the discrete levels, and found that the relaxation lifetime was about 10–100 ps.