Carrier dynamics for quantum dot (QD) heterosystem are the subject of intense material and device research. Photoexcitation dependence of inter-dot lateral carrier transport has been studied by temperature-dependent photoluminescence (PL). For comparison, two InAs/GaAs QD samples with different dot-size as well as size uniformity were carried out by metal-organic vapor phase epitaxy (MOVPE). Considering the thermal-sensitive PL spectra, the so-called V-shape behaviors were characterized to the corresponding carrier dynamic processes. At low temperatures, the full width at half maximum (FWHM) of 88 and 79 meV for the two QD samples, respectively, reveals that the optimal growth conditions improve the size uniformity. Meanwhile, the dot-size distribution is the dominant contribution to the inhomogeneous broadening of PL spectra. With increasing the temperatures as well as the excitation power, the so-called negative temperature phenomena are by far observed. The narrowing of the FWHM for all confined states is associated with the lateral thermally activated carrier transfer between inter-dots at the temperature range of 110 and 175 K. The photoexcited carriers have enough thermal energy not only to overcome the matrix barriers but also to redistribute to the local minimum states. Significantly, the thermalization of carriers in the less uniformity heterodot system is profound, while the better uniformity one exhibits more thermal-stability. As the temperature further increases, the FWHM of excited state extends once again, since both the electron-phonon scattering and thermal redistribution mechanisms dominate the carrier relaxation processes. All experimental results are consistent with the rate equation calculations as well. The observation of transmission electron microscopy images will be also shown.

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1. Intersublevel Relaxation Dependence of Carrier Hopping in self-organized InAs Quantum Dot Heterostructures