Red Luminesecnce from Self-Assembled InAlAs/AlGaAs Quantum Dots with Bimodal Size Distribution

Red-emitting at about 640nm from self-assembled In0.55Al0.45As/Al0.5Ga0.5As quantum dots grown on GaAs substrate by molecular beam epitaxy are demonstrated.A doublepeak structure of photoluminescence(PL)spectra from quantum dots was observed,and a bimodal distribution of dot sizes was also confirmed by an atomic force micrograph(AFM)image for uncapped sample.From the temperature and excitation intensity dependence of PL spectra,it is found that the double-peak structure of PL spectra from quantum dots is strongly correlated to the two predominant quantum dot families.Taking into account the quantum-size effect on the peak energy,it is proposed that the high(low)energy peak results from a smaller(larger)dot family,and this result is identical to the statistical distribution of dot lateral size from the AFM image.