Jan 14, 2010
InSb nanowires positioned for device applications
Researchers from Lund University (Sweden) have demonstrated the growth of perfectly vertical InSb nanowire arrays on standard substrate materials, despite extreme lattice mismatch between the nanowire and the substrate. In this approach, a nanowire stem is grown before initiating InSb growth to decouple it from the substrate. This makes it possible to extend the growth window of these nanowires to high temperatures to improve their crystal structure. InSb has the highest electron mobility of all semiconductors and promises fast and low-power future vertically integrated nanowire transistors.
Semiconductor nanowires are attractive materials for devices ranging from single photon sources to biosensors and vertical transistors. These tiny crystalline semiconducting needles could help to extend transistor downscaling due to the advantageous electrostatic coupling offered by the gate geometry. Another benefit is that their very small lateral dimensions (<50 nm) allow for efficient elastic strain relaxation when they are combined on different substrate materials.
Nanowire stem extends growth window
Now researchers at Lund University have taken the technology one step further with the introduction of a new nanowire material and its integration. The team studied nanowires made of InSb, which have been very seldom reported previously, and integrated them on standard substrates made of InAs, InP and GaAs using a metalorganic vapour phase epitaxy (MOVPE) reactor. InSb has the highest bulk electron mobility of 77,000 cm2 V–1s–1. A key result is that using a short stem of substrate material drastically improves the possibility to grow these nanowires under a wide range of conditions, where they do not normally grow. The nanowire template technology provides a larger temperature range, leading for instance to defect-free perfect InSb nanowires. A controlled array of these nanowires is shown in the figure above.
On a fundamental level, the extreme lattice mismatches investigated in this study (up to 14.6% mismatch for InSb/GaAs) should also favour new theoretical developments on elastic strain relaxation in axial nanowire heterostructures. Future work will include detailed experimental strain evaluations at the interfaces and realization of vertical devices.
The researchers presented their work in Nanotechnology.
About the author
Philippe Caroff, PhD, spent two years as a postdoctoral researcher at Lund University working on the growth of nanowires by MOVPE for vertical devices and the fundamental understanding of their crystal structure and tunability. Currently he holds a CNRS researcher position at Institut d'Electronique de Microélectronique et Nanotechnologie (IEMN) in Lille (France) where he has initiated MBE growth of III-V nanowires for nanoelectronic applications.