We present the monolithic integration and electrical characterization of InAs nanowires (NWs) with the well-defined geometries and positions on Si as a platform for quantum transport studies. Hereby, one-dimensional (1D) ballistic transport with step-like 1D conductance quantization in units of 2e2/h is demonstrated for NWs with the widths between 28 nm and 58 nm and a height of 40 nm. The electric field control of up to four individual modes is achieved. Furthermore, the sub-band structure of the nanowires is investigated using bias spectroscopy. The splitting between the first and the second sub-band increases as the width of the NWs is reduced, whereas the degeneracy of the second sub-band can be tuned by the symmetry of the NW cross section, in accordance with a “particle in a box” model. The length-dependent studies reveal ballistic transport for up to 300 nm and quasi-ballistic transport with a mean free path of 470 nm for longer InAs NW channels at 30 K. We anticipate that the ballistic 1D transport in monolithically integrated InAs NWs presented here will form the basis for sophisticated quantum wire devices for the future integrated circuits with additional functionalities.
III-V compound semiconductors are indispensable materials for today's high-end electronic and optoelectronic devices and are being explored for next-generation transistor logic and quantum technologies. III-V surfaces and interfaces play the leading role in determining device performance, and therefore, methods to control their electronic properties have been developed. Typically, surface passivation studies demonstrated how to limit the density of surface states. Strain has been widely used to improve the electronic transport properties and optoelectronic properties of III-Vs, but the potential of this technology to modify the surface properties still remains to be explored. Here we show that uniaxial stress induces a shift in the energy of the surface states of III-V nanowires, modifying their electronic properties. We demonstrate this phenomenon by modulating the conductivity of InAs nanowires over 4 orders of magnitude with axial strain ranging between -2.5% in compression and 2.1% in tension. The band bending at the surface of the nanostructure is modified from accumulation to depletion reversibly and reproducibly. We provide evidence of this physical effect using a combination of electrical transport measurement, Raman spectroscopy, band-structure modeling, and technology computer aided design (TCAD) simulations. With this methodology, the deformation potentials for the surface states are quantified. These results reveal that strain technology can be used to shift surface states away from energy ranges in which device performance is negatively affected and represent a novel route to engineer the electronic properties of III-V devices.
GaSb nanostructures integrated on Si substrates are of high interest for p-type transistors and mid-IR photodetectors. Here, we investigate the metalorganic chemical vapor deposition and properties of GaSb nanostructures monolithically integrated onto silicon-on-insulator wafers using template-assisted selective epitaxy. A high degree of morphological control allows for GaSb nanostructures with critical dimensions down to 20 nm. Detailed investigation of growth parameters reveals that the GaSb growth rate is governed by the desorption processes of an Sb surface layer and, in turn, is insensitive to changes in material transport efficiency. The GaSb crystal structure is typically zinc-blende with a low density of rotational twin defects, and even occasional twin-free structures are observed. Hall/van der Pauw measurements are conducted on 20 nm-thick GaSb nanostructures, revealing high hole mobility of 760 cm/(V s), which matches literature values for high-quality bulk GaSb crystals. Finally, we demonstrate a process that enables cointegration of GaSb and InAs nanostructures in close vicinity on Si, a preferred material combination ideally suited for high-performance complementary III-V metal-oxide-semiconductor technology.
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