Abstract
We present the growth and characterization of InAs quantum dots on Al x Ga 1− x As surfaces for intersubband devices. This requires the quantum dot energy levels in the Al x Ga 1− x As matrix to be above the GaAs bandedge. Using standard As 4 fluxes (beam equivalent pressure 8e−6 Torr), inhomogeneous broadening of the quantum dot size distribution increases with increasing Al content in the Al x Ga 1− x As matrix. Reducing the As 4 overpressure during In deposition is found to greatly improve the size distribution of the quantum dots, while producing slightly larger dots and a reduction in the density of small dots ( h<1.3 nm). Annealing at the higher standard As 4 flux for 30 s, after the reduced As 4 In deposition, produced a negligible change in the quantum dot size distribution. Utilizing surface dots on top of 30 layers of self-assembled quantum dots, the maximum quantum dot height for ground state energies above the GaAs bandedge is determined to be 2 nm for Al 0.30Ga 0.7As and 3 nm for Al 0.45Ga 0.55As.
Published Version
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