| AVS 56th International Symposium & Exhibition | |
| Surface Science | Monday Sessions |
| Session SS1+EM-MoA |
| Session: | Semiconductor Surfaces and Interfaces I: Ge and III-V's |
| Presenter: | M. Hjort, Lund University, Sweden |
| Authors: | M. Hjort, Lund University, Sweden A.A. Zakharov, Lund University, Sweden M.T. Borgström, Lund University, Sweden E. Hilner, Lund University, Sweden R. Timm, Lund University, Sweden A. Fian, Lund University, Sweden J.N. Andersen, Lund University, Sweden E. Lundgren, Lund University, Sweden L. Samuelson, Lund University, Sweden A. Mikkelsen, Lund University, Sweden |
| Correspondent: | Click to Email |
Self-assembled III-V nanowire heterostructures could be key components in many future optoelectronic devices [1], for example solar cells [2]. To realize photovoltaics from these structures variable p- and n-type doping along the nanowires are a fundamental prerequisite. The active component in solar cells, the pn-junction, has been grown axially in InP nanowires with different p- and n-type doping levels. However determining specific doping levels, effects of the nanowire surfaces and junction abruptness and band alignment across the interface with any precision is very difficult. Recently we have shown that scanning tunneling spectroscopy on nanowires with high resolution is possible [3] and we are now combining this with synchrotron based photoemission methods.
We have examined InP nanowires with up to two axial pn-junctions with Spectroscopic PhotoEmission and Low Energy Electron Microscopy (SPELEEM), X-ray Photoelectron Spectroscopy (XPS) as well as Scanning Tunneling Microscopy/Spectroscopy (STM/S). These techniques have given us the possibility to probe not only the structure of the nanowires but also the electrical properties (such as doping level) with high lateral resolution.
With our different setups we can probe the local density of states, atomic scale structure and work function differences along the wires. We can clearly distinguish between the different n- and p-type parts of the nanowires with both the scanning probe as well as with the synchrotron radiation based techniques. Both surface and the inner regions of the wires can to some extent be probed by varying photon energies in SPELEEM or modifying the surface for STM. This gives us the opportunity to understand the device at many different levels and improve its future quality.
[1]. L. Samuelson et al., Physica E 2004, 21, 560-567
[2]. M. T. Borgström et al., Nanotechnology 2008, 19, 445602
[3]. E. Hilner et al., Nano Letters 2008, 8 (11), 3978-3982