Using GaAs/AlGaAs self-assembled quantum dots we study the few-particle dynamics of fully confined systems, which is associated with purely Coulomb interaction and is not affected by the internal strain field. Systematic evolution in the binding energies of positive and negative trions, as well as biexcitons, with dot size is interpreted in terms of a balance between the Hartree mean-field corrections on single-particle states and the interparticle correlations which lead to a nonseparable dynamics. The experimental behaviors are well reproduced by exact many-body calculations within the framework of the quantum Monte Carlo approach. DOI: 10.1103/PhysRevB.82.201301 PACS number͑s͒: 78.67.Hc, 73.21.La, 78.55.Cr Excitons ͑X͒ and their multi-particles complexes, such as negative and positive trions ͑X − and X + , respectively͒ as well as biexcitons ͑XX͒, are prototypical few-body systems realized in a solid. Their simplest atomic counterparts, such as H − , which have been studied since the earliest days of quantum mechanics, are regarded as the system of choice for studying the intricacies of few-body dynamics.1 Particles in H − ͑two electrons and one proton͒ are bound due to a delicate balance between the attractive and repulsive interactions, and the relatively strong correlations reflecting low kinetic energies involved. Consequently, the dissociation energy of H − is only about 0.75 eV, much smaller than the ionization energy of the Hydrogen atom ͑13.6 eV͒.Quantum heterostructures, which accommodate charged particles in nanoscopic space, allow us to investigate the impact of dimensionality and localization on the few-particle dynamics. For quantum wells ͑QWs͒ in the strong confinement limit, the X binding energy ͑BE͒ would be enhanced by a factor of four compared to that in the three-dimensional system. The two-dimensional enhancement in the BE of XX ͑Refs. 2 and 3͒ as well as X Ϯ ͑Refs. 4 and 5͒ has been extensively studied. [6][7][8] Few-particle BEs in fully confined systems have been precisely determined by single quantum-dot ͑QD͒ spectroscopy experiments. Peculiar features reported so far show that for a common class of QDs the BE of X − is positive, 9 while that of X + is negative. 10 This is in stark contrast to higher dimensionality systems, where the bound states exist for both X − and X + in QWs, as well as for H − and H 2 + in nature. Moreover they show that the BE of XX becomes negative for sufficiently small QDs.11 Unbound XX is frequently observed in nitride polar QDs, 12 and, recently, in nonpolar QDs under in-plane strain. 13 These results suggest that fewparticle states are crucially influenced by the internal ͑piezo or spontaneous͒ electric field, which can be as high as the Coulomb field between charged particles.Various attempts using strained InGaAs QD systems have also shown that few-particle spectra depend heavily on the microscopic shape of each dot. Thus, in experiment, the size dependence of few-carrier levels has normally been observed with large scattering in data. This masked th...