InAs Heteroepitaxy on Nanopillar-Patterned GaAs (111)A

TL;DR

This study investigates InAs heteroepitaxy on nanopatterned GaAs(111)A substrates, demonstrating defect reduction and controlled nanostructure formation through substrate patterning and growth parameter optimization.

Contribution

It introduces a novel combination of nanosphere lithography and reactive ion etching to pattern GaAs(111)A substrates for improved InAs heteroepitaxy.

Findings

InAs forms nano-islands on pillar tops at low temperature and growth rate.

Higher growth rate increases island nucleation and hillock formation at pillar bases.

Concave pillar bases promote formation of merged hillocks or pyramids.

Abstract

Heteroepitaxy on nanopatterned substrates is a means of defect reduction at semiconductor heterointerfaces by exploiting substrate compliance and enhanced elastic lattice relaxation resulting from reduced dimensions. We explore this possibility in the InAs/GaAs(111)A system using a combination of nanosphere lithography and reactive ion etching of the GaAs(111)A substrate for nano-patterning of the substrate, yielding pillars with honeycomb and hexagonal arrangements and varied nearest neighbor distances. Substrate patterning is followed by MBE growth of InAs at temperatures of 150 - 350 C and growth rates of 0.011 nm/s and 0.11 nm/s. InAs growth in the form of nano-islands on the pillar tops is achieved by lowering the adatom migration length by choosing a low growth temperature of 150 C at the growth rate 0.011 nm/s. The choice of a higher growth rate of 0.11 nm/s results in higher InAs island nucleation and the formation of hillocks concentrated at the pillar bases due to a further reduction of adatom migration length. A common feature of the growth morphology for all other explored conditions is the formation of merged hillocks or pyramids with well-defined facets due to the presence of a concave surface curvature at the pillar bases acting as adatom sinks.