Pinholelike defects in multistack 1.3μm InAs quantum dot laser

The pinholelike defects often observed in multistack InAs quantum dot structures on GaAs have been investigated comprehensively. Due to the high surface stress of InAs quantum dots, the overgrowth of GaAs and InGaAs capping layers on InAs quantum dots is far from conformal and leads to the formation of these defects. Growth interruptions during GaAs spacer layer formation and thermal annealing after the GaAs growth are employed to completely eliminate the pinholelike defects in multistack quantum dot structures. Ridge-waveguide 1.32μm InAs quantum dot lasers prepared by this method exhibit internal quantum efficiency as high as 62%.