Selective control of In/sub 0.5/Ga/sub 0.5/As/GaAs quantum dot properties by rapid thermal processing: quantum dot intermixing

Recently, substantial reductions in the threshold-current-densities of quantum-dot (QD) lasers have been achieved, setting the scene for utilising devices containing QD structures. Initial work revealed the potential of preserving the 3D confinement of QDs even after annealing, and hence the possibility of post-growth control of the bandgap of these structures, allowing the integration of active and passive devices on the same chip. Selective control of the bandgap of laser diodes structures is necessary, however, for useful integration. Techniques originally developed for quantum well intermixing are investigated in the work as means of QD intermixing (QDI). The structure used in the work was a p-i-n separate confinement heterostructure grown using MBE and contained a single layer of self-organised In/sub 0.5/As/sub 0.5/As/GaAs QDs. Two intermixing techniques were investigated: impurity-free vacancy disordering (IFVD) using PECVD SiO/sub 2/ and irradiation damage induced intermixing using sputtered SiO/sub 2/. Samples annealed without any caps were also used as controls. All samples were annealed epi-layer down on a fresh piece of GaAs at different temperatures for 60 s. After etching the top contact layer and the upper cladding of the structure, PL measurements were carried out at 77 K using an Ar/sup +/ laser (/spl lambda/=514 nm).