Structural and optical behavior of strained InAs quantum boxes grown on planar and patterned GaAs (100) substrates by molecular-beam epitaxy

Strained, coherent InAs islands were grown on GaAs (100) planar substrates by molecular-beam epitaxy (MBE). These coherent islands were buried under GaAs cap layers grown by MBE and migration enhanced epitaxy at low temperature (approx. 400 °C), the latter case exhibiting an order of magnitude stronger photoluminescence (PL). The PL and PL excitation spectra reveal the discrete nature of the density of states of three-dimensionally confined electronic states in the islands. The possibility of placing InAs on a regular array of prepatterned square mesas, size-reduced via buffer layer growth to a ≤150 nm mesa top, was explored. The InAs on mesas with sub-100 nm lateral dimensions is found to have an enhanced critical thickness for two-dimensional to three-dimensional island morphology transition, going from approx.1.8 monolayers (ML) for growth on planar substrate to ≥5 ML for 70 nm mesas. Spectrally and spatially resolved cathodoluminescence studies show these InAs volumes to be optically active.