Growth, characterizations, theory and lasing of vertically stacked quantum dots

We investigate multiple sheets of self-organized InAs quantum dots (QDs) with thin GaAs spacer layers. The QDs spontaneously form on top of each other and couple electronically. In comparison to single sheets of QDs (SQDs), the coupling leads to lower energy levels and an expansion of the wavefunction. Thus carrier localization and gain increase. Three-dimensional strain distribution and electronic structure are theoretically modeled. Laser operation of vertically coupled quantum dots (VECOD's) improves largely as compared to SQD lasers and room temperature operation with a threshold of 680 A/cm/sup 2/ is obtained for a triple stack.