InAs heteroepitaxy on nanopillar-patterned GaAs (111)A

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.

Size‐Dependent Strain Relaxation in InAs Quantum Dots on Top of GaAs(111)A Nanopillars

“…For the formation of InAs islands on top of the nanopillars, a low growth temperature of 150 °C at a rate of 0.011 nm s −1 under As‐rich conditions (V/III ratio ≈400) was chosen. [ 13 ] The nominally deposited InAs thickness was between 2 and 15 nm.…”

“…[ 11 ] This has been accomplished by low‐temperature molecular beam epitaxial growth on nanopillar‐patterned GaAs, where the restricted adatom migration together with an enhanced nucleation rate of the second atomic layer on monolayer islands leads to QD formation on the pillar tops. [ 12,13 ] Since these QDs have steeper sidewalls than conventional InAs QDs grown at higher temperatures on planar GaAs(001), [ 14 ] a more efficient elastic strain relaxation and possibly an increased critical volume for misfit defect formation are expected. Another promising feature of InAs heteroepitaxy on GaAs(111)A is the absence of Ga/In alloying.…”

Strain-driven InAs island growth on top of GaAs(111) nanopillars

“…In order to obtain InAs growth on the nanopillars, a low growth temperature of 150°C at a rate of 0.011 nm/s under As-rich conditions (V/III ratio ~400) was chosen. 16 The nominally deposited InAs thickness was 15 nm.…”

“…Details on the patterning process can be found in a recent paper. 16 Heteroepitaxial growth of InAs on the nanopillar-patterned GaAs surface was performed by solid source molecular beam epitaxy after atomic H cleaning of the patterned substrate. In order to obtain InAs growth on the nanopillars, a low growth temperature of 150°C at a rate of 0.011 nm/s under As-rich conditions (V/III ratio ~400) was chosen.…”

“…In order to obtain InAs growth on the nanopillars, a low growth temperature of 150°C at a rate of 0.011 nm/s under As-rich conditions (V/III ratio ~400) was chosen. 16 The nominally deposited InAs thickness was 15 nm. Morphological and structural characterization of the heteroepitaxially overgrown substrates was performed by high-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging.…”