Theory of strain relaxation for epitaxial layers grown on substrate of a finite dimension

Nanoepitaxy of GaAs on a Si(001) substrate using a round-hole nanopatterned SiO2 mask

GaAs is grown by metal-organic vapor-phase epitaxy on a 55 nm round-hole patterned Si substrate with SiO(2) as a mask. The threading dislocations, which are stacked on the lowest energy facet plane, move along the SiO(2) walls, reducing the number of dislocations. The etching pit density of GaAs on the 55 nm round-hole patterned Si substrate is about 3.3 × 10(5) cm(-2). Compared with the full width at half maximum measurement from x-ray diffraction and photoluminescence spectra of GaAs on a planar Si(001) substrate, those of GaAs on the 55 nm round-hole patterned Si substrate are reduced by 39.6 and 31.4%, respectively. The improvement in material quality is verified by transmission electron microscopy, field-emission scanning electron microscopy, Hall measurements, Raman spectroscopy, photoluminescence, and x-ray diffraction studies.

Dislocation reduction of InAs nanofins prepared on Si substrate using metal-organic vapor-phase epitaxy

InAs nanofins were prepared on a nanopatterned Si (001) substrate by metal-organic vapor-phase epitaxy. The threading dislocations, stacked on the lowest-energy-facet plane {111}, move along the SiO2 walls, resulting in a dislocation reduction, as confirmed by transmission electron microscopy. The dislocations were trapped within a thin InAs epilayer. The obtained 90-nm-wide InAs nanofins with an almost etching-pit-free surface do not require complex intermediate-layer epitaxial growth processes and large thickness typically required for conventional epitaxial growth.

Critical thickness and radius for axial heterostructure nanowires using finite-element method

Finite-element methods are used to simulate a heterostructured nanowire grown on a compliant mesa substrate. The critical thickness is calculated based on the overall energy balance approach. The strain field created by the first pair of misfit dislocations, which offsets the initial coherent strain field, is simulated. The local residual strain is used to calculate the total residual strain energy. The three-dimensional model shows that there exists a radius-dependent critical thickness below which no misfit dislocations could be generated. Moreover, this critical thickness becomes infinity for a radius less than some critical values. The simulated results are in good agreement with the experimental data. The critical radius from this work is smaller than that obtained from previous models that omit the interaction between the initial coherent strain field and the dislocation-induced strain field.