SELF-ORGANIZED MICROSTRUCTURE GROWTH

We present evidence of the new phenomenon of the direct growth of microstructures by metal-organic vapor-phase epitaxy (MOVPE) on high-index GaAs substrates. One- and zero-dimensional self-faceting by step bunching on GaAs (n11)A substrates produces quantum-wire- and dot-like arrays on GaAs (311)A and GaAs (211)A substrates. The lateral periodicity of self-faceting is controlled by the layer thickness and growth temperature and is directly correlated with the red shift of the luminescence of GaAs/AlGaAs heterostructures. On GaAs (n11)B substrates, well-ordered quantum-dot arrays are formed in a new self-organizing growth mode found in the MOVPE of a sequence of AlGaAs and strained InGaAs films. The InGaAs film spontaneously interacts with AlGaAs buffer layers to form ordered arrays of disk-shaped InGaAs quantum dots buried within AlGaAs microcrystals due to lateral mass transport. The size and distance of the disks can be controlled independently by the In composition and the InGaAs layer thickness. Similar structures are also formed on InP (311)B substrates in the GaInAs/AIInAs and GaInAs/InP material systems. Lateral confinement of carriers in the disks is confirmed by the photoluminescence linewidth which, at room temperature, is as narrow as 13 meV due to reduced thermal broadening.