Fine structure and magneto-optics of exciton, trion, and charged biexciton states in single InAs quantum dots
Abstract
Recently, semiconductor quantum dots (QDs) have attracted considerable attention as they exhibit novel optical and electronic phenomena. In QDs, the interaction between electrons and holes becomes large, and excitons (one electron-hole pairs) are easily ionized. Therefore, not only the neutral quasiparticles, for example, excitons and biexcitons (two electron-hole pairs), but also several exciton complexes, for example, charged excitons (trions) and charged biexcitons can be created.
The authors measured photoluminescence spectra of individual InAs QDs by adopting high spatial resolution spectroscopy, and investigated detailed energy levels of the exciton complexes in strong-confinement system. Asymmetry of the QD structure induces anisotropic electron-hole exchange interaction, which results in the energy splitting of the exciton and excited trion states. Furthermore, by the measurement of magneto-PL spectroscopy in Faraday configuration, they observed Zeeman splitting and diamagnetic shifts. The diamagnetic coefficient of the charged biexciton emission line shows the larger variation compared to that of the other complexes, although it should be the same value. On the other hand, the variation of the effective g factors for the exciton complexes are caused by the difference of the extension of the carrier wavefunctions, which depend on the shape and size of the QDs. In particular, the effective g factor changes sensitively by the difference between the extension of p-wavefunction for the electron and that for the hole.