Selective Nucleation of GaAs on Si Nanofacets

Journal of Electronic Materials, 2001

Journal of Crystal Growth, 2002

Dynamical faceting during homoepitaxial growth of GaAs on nanoscale-patterned surfaces by molecular beam epitaxy is examined. Selective deposition on open GaAs(1 0 0) surfaces with lateral dimensions ranging from 130 to 250 nm, separated by 15-80 nm-wide (25-nm-thick) SiO 2 stripes aligned along the ½0 % 1 1 direction results in facet formation and lateral growth over the SiO 2 mask. At the early stage of growth, (3 1 1) facets appear on sidewalls near the boundary between an open GaAs surface and SiO 2 mask, these are replaced by (1 1 1) facets starting from SiO 2 boundaries as growth continues. After complete replacement, growth proceeds laterally in the direction perpendicular to ½0 % 1 1 retaining the (1 1 1) facets until coalescence occurs between adjacent triangular cross-sectioned GaAs stripes. Nanoscale fabrication nonuniformity results in dynamical formation and retention of multiple (3 1 1) facets even for growth thicknesses much greater than the thickness of the SiO 2 mask stripes. This dynamical faceting is interpreted by minimization of total surface free energy based on equilibrium crystal shape, in qualitative agreement with our experimental results. r

Journal of Applied Physics, 2016

Three-dimensional, epitaxial GaAs crystals are fabricated on micro-pillars patterned into Si(001) substrates by exploiting kinetically controlled growth conditions in Molecular Beam Epitaxy. The evolution of crystal morphology during growth is assessed by considering samples with increasing GaAs deposit thickness. Experimental results are interpreted by a kinetic growth model, which takes into account the fundamental aspects of the growth and mutual deposition flux shielding between neighboring crystals. Different substrate pattern geometries with dissimilar lateral sizes and periodicities of the Si micro-pillars are considered and self-similar crystal structures are recognized. It is demonstrated that the top faceting of the GaAs crystals is tunable, which can pave the way to locally engineer compound semiconductor quantum structures on Si(001) substrates.

Applied Physics Letters, 2008

The faceting of a quasi-two-dimensional nanoscale crystal ͑quasi-2D nanocrystal͒ grown by metal-organic vapor phase epitaxy is reported. Homoepitaxial selective growth is performed on a 200 nm wide, ͓110͔-directed stripe opening fabricated in a 30 nm thick SiO 2 film atop a GaAs͑001͒ substrate. In the cross section perpendicular to the stripe opening, a selectively grown epilayer is regarded as a quasi-2D nanocrystal, which is close to a hexagonal shape symmetrically surrounded with ͑111͒B-, ͑110͒and ͑111͒A-type facets from the top as growth proceeds both vertically and laterally. The resulting faceting is interpreted on the basis of equilibrium crystal shape ͑ECS͒. The comparison of the observed crystal shape with theoretical modeling enables the measurement of the relative surface energies of the low index orientations. The ECS of a GaAs 2D crystal under the given growth conditions is proposed.

IEEE Journal of Photovoltaics, 2018

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2014

The authors report the molecular beam epitaxial growth and the structural and optical characterizations of self-assembled/catalyst-free GaAs nanodisks on SiO 2 masked Si(100) patterned substrates. Pure zincblende GaAs nanodisks with precise positioning and low defect density are demonstrated by selective area epitaxy. The influence of the growth temperature and deposition duration is investigated. Excellent morphological and structural properties are characterized by scanning electron microscopy and cross-sectional transmission electron microscopy. Defects in the epilayers are reduced by strain relaxation through facets formation and by a lateral overgrowth scheme atop the SiO 2 mask which is corroborated by microRaman spectroscopy. In particular, the authors show how the material quality contributes to excellent optical properties observed by microphotoluminescence spectroscopy from 77 K to room temperature. V

Journal of Applied Physics, 1999

The growth selectivity on patterned GaAs (311)A substrates differs qualitatively from that on low-index (100) and (111) substrates. During molecular beam epitaxy of (Al,Ga)As, [01-1] oriented mesa stripes develop a fast growing convex sidewall. A continuous transition occurs towards the slow growing concave sidewall upon turning the mesa along the perpendicular [-233] direction without breaking up the growth front into microfacets. This allows their systematic combination at the corner or edge of intersecting mesa stripes appropriately inclined from [01-1] among which we highlight those involving fast growing sidewalls. The scenario, which is unique for patterned GaAs (311)A substrates, offers a novel degree of flexibility for the design of lateral functional semiconductor nanostructures.

Materials Science and Engineering: B, 1991

We report on the fabrication of a composite GaAs-SiO 2 nucleation layer. The layer is formed by a deposition of a GaAs island layer by molecular beam epitaxy (MBE), followed by an oxidation step of the silicon regions surrounding the islands. In this way, small GaAs islands, for which the critical thickness for misfit dislocation generation is increased, are surrounded by a stable amorphous phase. Lateral overgrowth seeded by the individual GaAs islands might enhance the overall epilayer quality. We describe the fabrication and cleaning of such a composite GaAs-SiO x nucleation layer that is compatible with the epitaxy process. Preliminary regrowth on a non-optimized composite surface resulted in GaAs-on-silicon quality equal to standard GaAs-on-silicon. Compared with GaAs epitaxy on porous silicon, another seeded growth technique, the composite surface technique has greater technological potential for the monolithic integration of GaAs and silicon electronics. 0921-5107/91/$3.50

Journal of Applied Physics, 2004

High-quality and defect-free GaAs were successfully grown via molecular beam epitaxy on silicon dioxide patterned Si(111) substrates by a two-step growth technique. Compared with the one-step approach, the two-step growth scheme has been found to be a better pathway to obtain a superior-quality GaAs on Si. Taking advantages of low energy for both Si(111) surface and GaAs/Si(111) interface, the two-step grown GaAs of total 175 nm atop patterned Si(111) substrates exhibits atomically smooth surface morphology, single crystallininty and a remarkably low defect density. A low-temperature GaAs nucleation layer of the two-step growth helps relieve the misfit stress by accommodating the misfit dislocations at the very adjacent GaAs/Si interface. The excellent properties of the two-step grown GaAs were investigated and verified by field-emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Finally we demonstrated a GaAs on Si solar cell, which could represent an important milestone for future applications in light-emitting diodes, lasers, and photodetectors on Si.