MOLECULAR-BEAM EPITAXY GROWTH OF QUANTUM DOTS FROM STRAINED COHERENT UNIFORM ISLANDS OF INGAAS ON GAAS

The two- (2D) to three-dimensional (3D) growth mode transition during the initial stages of growth of highly strained InGa1-xAs on GaAs is u sed to obtain quantum dot structures. Transmission electron micrograph s (TEM) reveal that when the growth of InxGa1-xAs is interrupted exact ly at the onset of this 2D-3D transition, dislocation-free islands (do ts) of InGaAs result. Size distribution measurements from TEM images i ndicate that these dots are less than 300 angstrom in diameter and rem arkably uniform. A phase diagram is constructed, showing the growth co nditions under which these strained coherent uniform dots form. Photol uminescence from layers containing these dots is observed and correlat ed with growth conditions and with structural data obtained from TEM i mages. We observe that the photoluminescence emitted from the dots and an underlying reference quantum well are nearly equal, indicating a h igh quantum efficiency for these quantum dots.