Nonuniform carrier trapping among quantum dots

In quantum-dot (QD) structures, carriers do not distribute uniformly among QDs. Carriers tend to distribute at larger QDs. Combined with state filling effect, carrier will populate larger QDs first. Then, carrier will populate smaller QDs at higher injection density. The nonuniform carrier distribution also leads to the separation of two emission peaks with increasing current. On the fabricated devices, the photon energy difference between the two peaks increased from 70.8 meV at 60 mA to 78 meV at 160 mA. By observing the peak separation, the tendency of carrier distribution can be identified.