Highly lattice mismatched InP/Si nanowire heterostructures were synthesized using metal organic chemical vapor deposition (MOCVD) process at 450 ºC. The InP nanowire diameter as high as 500 nm is much thicker than the critical diameter (~24 nm for InP/Si) predicted by a recent theoretical work on the coherent growth of nanowire heterostructures. We investigated possible factors that lead to the unusually large diameters in a highly lattice mismatched material system. Dislocations formed at the interfacial plane of the heterostructure due to high lattice mismatch were found to contribute to the growth of nanowires with very large diameters. An extra pair of dislocation lines at the interfacial plane was found to support an increase in nanowire diameter by ~12 nm.
Low temperature metal catalyzed InP nanowires with diameters ranging from 50nm to 500nm using a single step
MOCVD process at 450°C on (111)-oriented silicon substrates have been synthesized. The diameter range is much
higher than the critical limit (~24nm for InP on silicon) reported by a recent theoretical work on coherent growth of
nanowire heterostructures. This article presents the results of our investigation to highlight the possible factors that lead
to the unusually large diameters and help realize stable nanowire heterostructures in a highly lattice mismatched material
system. Our analysis finds dislocations formed at the interfacial plane of the heterostructure due to high lattice mismatch
is the most influential factor contributing to very large diameters. We have simulation results which indicate that each
added pair of orthogonal dislocation lines at the interfacial plane between InP and silicon supports ~12nm increase in the
nanowire diameter. A maximum nanowire density of ~5×108 cm<sup>-2</sup> is estimated with growth rates ranging from 0.1
µm/min for the shortest nanowires and 10 μm/min for the longest ones.
We demonstrate an InP nanowire based photodetector laterally integrated between two (111)-oriented vertical silicon surfaces. The nanowires are grown through a simple single step chemical vapor deposition (CVD) process using gold nanoparticles as catalyst with
in-situ p-doping and have been heteroepitaxially bridged between a pair of prefabricated p-doped Si electrodes. Nonlinear current-voltage characteristics are observed. Although this nonlinearity resembles a back-to-back rectifying profile it originates from space-charge limited conductivity of the nanowires. DC photoelectric characteristics of the device were measured under optical illumination (λ=630 nm) above the bandgap energy (1.34 eV or ~925 nm at room temperature) of InP. The variation in photoconductance with varying input optical power demonstrates high sensitivity of the device to optical illumination.
Conference Committee Involvement (2)
Nanomaterials Synthesis, Interfacing, and Integrating in Devices, Circuits, and Systems II
9 September 2007 | Boston, MA, United States
Nanomaterial Synthesis and Integration for Sensors, Electronics, Photonics, and Electro-Optics
1 October 2006 | Boston, Massachusetts, United States