Regaining a Spatial Dimension: Mechanically Transferrable Two-Dimensional InAs Nanofins Grown by Selective Area Epitaxy

Abstract

We report a method for growing rectangular InAs nanofins with deterministic length, width and height by dielectric-templated selective-area epitaxy. These freestanding nanofins can be transferred to lay flat on a separate substrate for device fabrication. A key goal was to regain a spatial dimension for device design compared to nanowires, whilst retaining the benefits of bottom-up epitaxial growth. The transferred nanofins were made into devices featuring multiple contacts for Hall effect and fourterminal resistance studies, as well as a global back-gate and nanoscale local top-gates for density control. Hall studies give a 3D electron density 2.5 − 5 × 10 17 cm −3 , corresponding to an approximate surface accumulation layer density 3 − 6× 10 12 cm −2 that agrees well with previous studies of InAs nanowires. We obtain Hall mobilities as high as 1200 cm 2 /Vs, field-effect mobilities as high as 4400 cm 2 /Vs and clear quantum interference structure at temperatures as high as 20 K. Our devices show excellent prospects for fabrication into more complicated devices featuring multiple ohmic contacts, local gates and possibly other functional elements, e.g., patterned superconductor contacts, that may make them attractive options for future quantum information applications.Quantum devices were underpinned for several decades by the interfacial two-dimensional (2D) electron gas found in III-V semiconductor heterostructures. 1 A top-down approach to these systems is costly, with heterostructure complexity limited by interfacial strain issues.Bottom-up approaches have thus generated massive interest with a heavy focus on onedimensional (1D) nanostructures, i.e., nanowires, where small interfaces enable greater heterostructure versatility, including the ability to integrate III-Vs on low-cost Si substrates. [2][3][4] Researcher ingenuity has meant clever new devices still arise from the nanowire geometry even after two decades. That said, we suspect we are not alone in wishing for extra spatial dimensions to work with. An attractive idea would be to take the hexagonal nanowire cross-section and stretch it to obtain a 2D 'nanofin' such that two side-facets have much larger area. These could be transferred to a separate substrate to make devices featuring, e.g., multiple contacts and gates by conventional nanofabrication methods. This concept is impossible with vapor-liquid-solid approaches. 5,6 Here we demonstrate it is possible using selective-area epitaxy, 7,8 giving 2D InAs nanofins with precise size control, and opening a path to more interesting nanostructure shapes via appropriate mask design. 9Our 2D nanofins offer some interesting potential for nanoelectronics. Firstly, they offer

Rotated domains in selective area epitaxy grown Zn3P2: formation mechanism and functionality

“…16,23–25,29–32 The small interface area helps to limit the formation of interface related defects, and the shape of the nanostructure can be controlled by the geometry of the openings. 16,29,33,34 While this helps minimise the interface related defects, there are other sources of defects in Zn 3 P 2 . 35–38 Various defect levels in the bandgap have been experimentally probed by various groups previously, but very few have been able to describe the exact origins.…”

Microscopic Understanding of the Growth and Structural Evolution of Narrow Bandgap III–V Nanostructures

“…In 2019, Sasa Gazibegovic et al grew InSb nanosheets directly from a InSb substrate platform without any foreign stem formation [ 64 ]. With a SiO x dielectric template fabricated by a mask transfer process by the plasma-enhanced CVD, the rectangular InAs nanofins with definite length, width and height can be synthesized at the rectangular opening using the MOCVD method ( Figure 5 c) [ 63 ]. By controlling the In flux, the morphology of InAs can be adjusted from 1D NWs to 2D nanosheets ( Figure 5 d) [ 28 ].…”

Understanding Shape Evolution and Phase Transition in InP Nanostructures Grown by Selective Area Epitaxy

“…[8] These drawbacks motivate the exploration of 2D and 3D nanostructures with sophisticated shapes and more functionalities. [9][10][11][12][13][14][15][16][17][18][19][20] For instance, Chi et al [21] reported twin-free GaAs nanosheets which have the advantage of membranelike geometry over nanowires in realizing crystal perfection. 2D and 3D nanostructures also present superior material performance, such as enhanced light scattering and second harmonic generation in V-shaped InAs nanomembranes, [22,23] large-scale emission homogeneity of InP nanorings, InP and GaAs nanomembrane arrays, [4,24] outstanding quantum transport and electronic properties of InSb nanosheets, [25][26][27][28] and reduced piezoelectric field inside InGaN quantum wells grown on nonpolar sidewalls of GaN nanosheets.…”

“…[19,29] Furthermore, the larger dimensions also make device fabrication easier. [10,27,28] More recently, complex III-V networks grown by SAE technique are extensively investigated because of their great potential in quantum science. [20,[30][31][32][33][34] All these works show the significance of shape engineering in fundamental research and device applications from diverse perspectives.…”

“…[ 8 ] These drawbacks motivate the exploration of 2D and 3D nanostructures with sophisticated shapes and more functionalities. [ 9–20 ] For instance, Chi et al. [ 21 ] reported twin‐free GaAs nanosheets which have the advantage of membrane‐like geometry over nanowires in realizing crystal perfection.…”