Layer-by-layer and step-flow growth mechanisms in GaAsP/GaP nanowire heterostructures
- PDF / 266,712 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 61 Downloads / 219 Views
C. Fradin Department of Physics and Astronomy and Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4M1, Canada
R.R. LaPierrea) Centre for Emerging Device Technologies, Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7, Canada (Received 3 April 2006; accepted 19 May 2006)
GaP–GaAsP segmented nanowires (NWs), with diameters ranging between 20 and 500 nm and lengths between 0.5 and 2 m, were catalytically grown from Au particles on a GaAs (111)B substrate in a gas source molecular beam epitaxy system. The morphology of the NWs was either pencil-shaped with a tapered tip or rod-shaped with a constant diameter along the entire length. Stacking faults were observed for most NWs with diameters greater than 30 nm, but thinner ones tended to exhibit fewer defects. Moreover, stacking faults were more likely found in GaAsP than in GaP. The composition of the pencil NWs exhibited a core–shell structure at the interface region, and rod-shaped NWs resulted in planar and atomically abrupt heterointerfaces. A detailed growth mechanism is presented based on a layer-by-layer growth mode for the rod-shaped NWs and a step-flow growth mode for the tapered region of the pencil NWs.
I. INTRODUCTION
There has been much interest recently in the vapor– liquid–solid (VLS) process for the “bottom-up” growth of semiconductor nanowires (NWs). In the VLS growth process, precursor source material is transported to a substrate that is seeded with small metal particles (usually Au). Preferential nucleation occurs at the Ausemiconductor interface, resulting in the growth of onedimensional semiconductor NWs. These structures have been used successfully as building blocks in the assembly of devices such as bipolar junction transistors and logic gates,1,2 single-electron memory devices,3 p-n diodes,4 and double barrier resonant tunneling diodes.5 Silicon NW field effect transistors capable of detecting DNA and single virus particles have also recently been demonstrated.6,7 Various photonic nanosystems consisting of photonics crystals, integrated NW lasers, lightemitting diodes, waveguides, and modulators have all been fabricated by the VLS method.8–11 Device applications obviously require rational control
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0341 J. Mater. Res., Vol. 21, No. 11, Nov 2006
http://journals.cambridge.org
Downloaded: 12 Oct 2015
of the NW morphology, which may be achieved by alternating between conditions that promote uncatalyzed radial growth on the NW sidewalls as compared to catalytic axial growth.12,13 In this way, a variety of nanowire shapes may be produced (intentionally or otherwise) including straight rods, tapered rods, and conical structures. In addition to controlling the morphology of NWs, one-dimensional quantum electronic devices require the implementation of heterostructures, whereby the distribution of chemical elements changes abruptly along the axis or radius of the NW. Device
Data Loading...
