Fabrication of strained InAs island ensembles on nonplanar patterned GaAs(001) substrates

Abstract

We report on the behavior of InAs deposited on nonplanar GaAs(001) substrates patterned with ≲0.5 μm wide stripe mesas oriented along the [11̄0] and 〈100〉 directions and with square mesas with a lateral size of ≳0.5 μm oriented along the 〈100〉 directions. Interfacet migration of In from the sidewalls to the mesa top leads to an enhanced InAs island density on the stripe as well as square mesa tops compared to that on the planar unpatterned region. Using such interfacet migration and InAs deposition amount less than needed for island formation on planar GaAs(001), we demonstrate complete selectivity in the positioning of InAs islands on the [11̄0] oriented stripe mesas of widths ≲100 nm, with islands forming exclusively on the mesa tops. These islands arrange in mesa-width-dependent parallel chains. They show photoluminescence (PL) comparable to that from the islands on the planar substrates. The polarization dependence of the PL suggests the presence of anisotropy in strain fields and potential elongation of islands in the [11̄0] direction. The significance of the stripe mesa edge orientation to the island formation is revealed by vastly different island densities and InAs morphology on the [11̄0] oriented versus 〈100〉 oriented stripe mesas. These differences reflect difference in migration from the different sidefacets that surround the (001) mesa top.