InAs/InP Radial Nanowire Heterostructures as High Electron Mobility Devices

Abstract

Radial core/shell nanowires (NWs) represent an important class of one-dimensional (1D) systems with substantial potential for exploring fundamental materials electronic and photonic properties. Here, we report the rational design and synthesis of InAs/InP core/shell NW heterostructures with quantum-confined, high-mobility electron carriers. Transmission electron microscopy studies revealed single-crystal InAs cores with epitaxial InP shells 2−3 nm in thickness, and energy-dispersive X-ray spectroscopy analysis further confirmed the composition of the designed heterostructure. Room-temperature electrical measurements on InAs/InP NW field-effect transistors (NWFETs) showed significant improvement in the on-current and transconductance compared to InAs NWFETs fabricated in parallel, with a room-temperature electron mobility, 11 500 cm 2 /Vs, substantially higher than other synthesized 1D nanostructures. In addition, NWFET devices configured with integral high dielectric constant gate oxide and top-gate structure yielded scaled on-currents up to 3.2 mA/µm, which are larger than values reported for other n-channel FETs. The design and realization of high electron mobility InAs/InP NWs extends our toolbox of nanoscale building blocks and opens up opportunities for fundamental and applied studies of quantum coherent transport and high-speed, low-power nanoelectronic circuits.Central to the "bottom-up" vision for nanoscale science and technology is the design and rational synthesis of building blocks with well-defined physical properties. 1 Semiconductor NWs represent a broad class of one-dimensional (1D) building blocks in which significant progress is being made in atomic to nanometer scale control of materials morphology, size, and composition, 1-4 including the growth of axial, 2 radial, 3 and branched 4 NW heterostructures. In the case of radial NW heterostructures, 3,5a-c the controlled growth of one or more shells can passivate existing surface states, enable new interface properties, and introduce unique electronic and photonic function. For example, the energy band line-up at the Ge and Si interface of Ge/Si core/shell NWs 5 leads to the accumulation of high-mobility hole carriers, which have enabled fundamental studies of quantum transport 5a,b and the realization of the highest performance p-channel NWFETs to date. 5c There has also been considerable effort placed on developing high electron mobility NWs with InAs, which has a small electron effective mass and correspondingly high bulk electron mobility, 6 the focus of a number of groups. 7 Reported electron mobilities for InAs NWs have been substantially lower than bulk values 7 and thus suggest that scattering processes in the NWs, including ionized impurity and surface scattering, 7d reduce mobility. Hence, structures that passivate and/or protect the surface of InAs NWs might lead to enhanced transport properties. To this end, we report studies of InAs/InP core/shell NWs in which the InAs surfaces have been passivated with a nanometer-thick ep...

Mobility Enhancement by Sb-mediated Minimisation of Stacking Fault Density in InAs Nanowires Grown on Silicon

“…The mobility starts to saturate at lower temperature at which point it becomes limited by scattering events related to the nanowire structure including planar defects. 15 Similar trends have been observed previously in InAs films, 42 InAs nanowires 15 and InAs-InP 43 and InAs-InAlAs 44 core-shell nanowires. Here we consider three different candidate mechanisms that could be causing this marked increase in mobility with antimony content: (i) the different intrinsic electrical properties of InAs 1−x Sb x as a function of Sb content; (ii) the different electrical properties of the WZ and ZB polytypes of InAs 1−x Sb x ; and (iii) the variation of the planar defect density.…”

Polarity driven formation of InAs/GaAs hierarchical nanowire heterostructures

“…10 Nanowire heterostructures can be produced by modulating the composition of a nanowire axially 11 and radially. 12 Radial nanowire heterostructures consist of core and shell ͑or multishell͒ morphologies, which offer flexibility to engineer the band gaps of a radial nanowire heterostructure and thereby, desired properties can be obtained. 13,14 Many potential applications have been demonstrated using these radial nanowire heterostructures including multicolor light-emitting diodes, 14 address decoders, 15 high electron mobility transistors, 16 and nonvolatile crossbar switches.…”

The 2008 Kavli Prize in Nanoscience: Carbon Nanotubes

“…44 Since then, Lieber and others have demonstrated the syntheses of a wide range of NW materials, including heterostructures (Figure 4) [45][46][47] with advanced and well-defined functionalities and properties while controllably assembling them into hierarchical structures ( Figure 5) and configuring them for a wide range of applications. [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] Properties and Applications. While the material properties of carbon nanotubes are primarily governed by their chirality (and thus, their diameter), for NWs, the properties are tuned by both the diameter and the elemental composition, which adds another handle in controlling functionality.…”

“…However, high-mobility p-type ( h Ϸ 750 cm 2 /(V · s)) and n-type ( n Ϸ 10000 cm 2 /V · s) transistors based on Ge/Si core/shell and InAs NWs have been demonstrated for diameters of 10Ϫ25 nm. 49,50,52 While there is no clear evidence for increased carrier mobilities over their bulk counterparts, the reduced dimensions of NWs result in improved gate coupling and reduced short channel effects, which are critical for achieving high performance in nanoscale devices. Additionally, NW heterostructures can be readily synthesized with controlled dimensions and elemental composition for enhanced transport properties as has been shown in the Ge/Si and InAs/InP core/shell NW structures.…”

“…Additionally, NW heterostructures can be readily synthesized with controlled dimensions and elemental composition for enhanced transport properties as has been shown in the Ge/Si and InAs/InP core/shell NW structures. 49,50 Another unique advantage of NWs for electronics is the ability either to grow NWs directly on Si substrates or first to grow and then to transfer them to receiver substrates for heterogeneous integration, 53 without encountering the lattice mismatch difficulties often faced for planar films. Furthermore, the low processing temperatures for crystalline NWs enable multilayer stacking of high-performance electronic and sensor elements for multifunctional, 3-D integration.…”