| Recent developments in the growth of self-organized quantum dots have provided opportunity to investigate the physics of zero-dimensional quantum structure. In this work, we investigate the carrier dynamics in the In(Ga)As/(A1)GaAs self-organized quantum dots using time-resolved photoluminescence and pump-and-probe spectroscopy. Three areas of carry dynamics are studied: radiative recombination, thermionic emission, and carrier relaxation. The measured radiative lifetime is compared to the published results. A reduced radiative transition rate is found. This increase in the PL decay time can be attributed to the localization of the exciton in the quantum dot. From the temperature dependent measurement, we find that the reduction of quantum dot photoluminescence efficiency at high temperature is attributed to the thermionic emission. The effect of thermionic emission process can significantly modify the potential quantum dot device properties such as optical gain and modulation bandwidth. From the transient absorption measurement, a fast carrier relaxation rate is deduced. The measured carrier relaxation time is an order of magnitude smaller than the theoretical prediction of the phonon bottleneck, indicating an other relaxation mechanism might be dominant in these quantum dots. |
