Optical properties of single charge tuneable InGaAs quantum dots

We present a magneto-optical investigation of neutral and charged few-exciton complexes in individual In0.5Ga0.5As self-assembled quantum dots. The results reveal direct information regarding Coulomb interaction and correlation effects in dots containing a controlled number of excess electrons (Ne=0,1,2,3,4) or holes (Nh=0,1,2). Either red or blue shifts of the emission energy are observed as the dot is loaded with excess electrons or holes, respectively. These observations are discussed in terms of the expected nature of the few-particle wave functions. In addition complementary magneto-optical measurements have been performed for negatively charged dots. With increasing Ne a weak increase of the g-factor and a strong reduction of the diamagnetic shift is observed. A pronounced minimum of the diamagnetic shift occurs for Ne=3.