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

Abstract

We analyze the shape and position of heteroepitaxial InAs islands on the top face of cylindrical GaAs(111)A nanopillars experimentally and theoretically. Catalyst-free molecular beam epitaxial growth of InAs at low temperatures on GaAs nanopillars results in InAs islands with diameters < 30 nm exhibiting predominantly rounded triangular in-plane shapes. The islands show a tendency to grow at positions displaced from the center towards the pillar edge.Atomistic molecular statics simulations evidence that triangular-prismatic islands centered to the pillar axis with diameters smaller than that of the nanopillars are energetically preferred.Moreover, we reveal the existence of minimum-energy states for off-axis island positions, in 2 agreement with the experiment. These findings are interpreted by evaluating the spatial strain distributions and the number of broken bonds of surface atoms as a measure for the surface energy. The influence of surface steps on the energy of the system is addressed as well.

Spontaneous shape transition of MnxGe1−x islands to long nanowires

“…However, islands of Mn-rich Ge-Mn phases could easily nucleate on the surface upon high-temperature annealing of the Mn wetting layer. At low Mn thicknesses, small islands are expected to be strained and their nucleation onto the film surface occurs during the early stage of the annealing process, driven by strain between the epilayer and the substrate as detected in several heteroepitaxial systems, such as Ge on Si [42][43][44], InAs on GaAs [45], Co silicide [36], and silicides with different metals [35]. Such a mechanism is expected to occur in our Mn layers deposited on Ge(111) substrates, due to the large lattice mismatch between Mn and Ge.…”

Selective Area Growth of Cubic Gallium Nitride in Nanoscopic Silicon Dioxide Masks

“…Patterning of larger areas (A > 2 Â 2 cm 2 ) was done by NSL and BCP. [17][18][19] Resulting masks consisted of hexagonally close-packed holes. The processes were designed to yield nominal hole diameters of 130 nm (NSL) and 17 nm (BCP).…”

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

“…For both InAs and GaAs cylindrical morphologies with dimensions corresponding to the experiments for deposited InAs thicknesses of 2 and 5 nm were chosen ( Figure ). A cylindrical shape has been assumed because it is similar to the rounded triangular InAs island shape found by scanning electron microscopy imaging for 15 nm deposited thickness, [ 11 ] and because for smaller deposited thicknesses, i.e., smaller island size the triangular shape is expected to be less stable from an energetic viewpoint. If present in the experiment, 60° misfit dislocations were inserted at the heterointerface as follows.…”

“…In order to reduce the heavily strained InAs volume and interdiffusion phenomena, InAs growth on GaAs(111)A nanopillar tops appears to be an alternative worth considering. [ 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.…”

“…[10] In order to reduce the heavily strained InAs volume and interdiffusion phenomena, InAs growth on GaAs(111)A nanopillar tops appears to be an alternative worth considering. [11] This has been accomplished by low-temperature molecular beam epitaxial growth on nanopillar-patterned GaAs, where the component of b, and w InAs the width of the InAs island at the heterointerface. [22] As with misfit dislocations at axial heterointerfaces in GaAs/GaSb (111)B nanowires having a similar lattice mismatch, [23] the Burgers vector lies in the heterointerface plane.…”