Luminescence Excitation Spectroscopy of InAs/InGaAs/GaAs Quantum-Dot Arrays in the Temperature Range between 20 and 300 K

Abstract

Evolution of photoluminescence (PL) and PL excitation spectra in structures containing InAs/InGaAs/GaAs quantum-dot (QD) arrays is investigated in detail as a function of detection energy in the temperature range from 20 to 300 K. Detailed analysis of PL excitation spectra enabled identification of peaks corresponding to excited QD states. The transition probability from the latter to the ground state is higher than in states the transition probability from which to the ground state is low but considerably increases due to effective carrier relaxation involving LO phonons. The dependence of the energy difference of the spectral position of the peaks corresponding to the ground and excited states on ground-state energy (i.e., on QD size) that is characteristic for QDs is found to be violated at 140–160 K, the temperature at which transport of carriers between QDs becomes activated.