| AVS 63rd International Symposium & Exhibition | |
| Electronic Materials and Photonics | Wednesday Sessions |
| Session EM+NS+SP+SS-WeA |
| Session: | Nanoscale Imaging of Metals and Compound Semiconductor based Nanostructures, Surfaces and Interfaces |
| Presenter: | Rainer Timm, Lund University, Sweden |
| Authors: | J. Knutsson, Lund University, Sweden S. McKibbin, Lund University, Sweden M. Hjort, Lund University, Sweden J. Colvin, Lund University, Sweden S. Yngman, Lund University, Sweden A. Troian, Lund University, Sweden O. Persson, Lund University, Sweden A. Mikkelsen, Lund University, Sweden R. Timm, Lund University, Sweden |
| Correspondent: | Click to Email |
III-V semiconductor nanowires (NWs) have a large technological potential within electronics, optoelectronics, and energy harvesting [1]. With their flexibility in creating heterostructures, by radial and axial stacking during epitaxial growth, comes an increasing complexity of device structure. Furthermore, due to their small diameter and their very large surface-to-volume-ratio, the performance of NW devices is strongly determined by surface properties. It is therefore essential to study the structural and electronic properties of NW surfaces down to the atomic level and across interfaces regarding doping, material composition, or crystal phase.
We recently obtained atomically resolved scanning tunneling microscopy (STM) images of various GaAs, InAs, and InP NW surfaces [2,3]. By combining STM imaging with scanning tunneling spectroscopy (STS) measurements, we correlate the surface structure and local electronic properties [3]. Here, we will present examples from InAs NWs with interfaces between different crystal phase. Our low-temperature STM/S results show that even the smallest possible insertion of zincblende phase within a wurtzite segment, a single bilayer stacking fault, shows a clear zincblende signature. We observe transitions in the local density of states with sub-nm lateral resolution. Furthermore, we map the interface band alignment and measure quantum confinement energies of single and double bilayer stacking faults.
Beyond traditional steady-state surface characterization, it is desirable to even investigate nanostructure devices in-situ, meaning while they are operating under an applied bias. We are now using simultaneous STM, AFM, and electrical transport measurements for studying individually contacted NWs during device operation [4], complemented by Kelvin probe force microscopy and scanning photoemission microscopy. We will present initial results of such combined in-situ studies on axial pn-junctions in InP and GaInP NWs, where we also investigate the influence of NW surface modification (e.g. removal of native oxide by atomic hydrogen) on photovoltaic properties.
[1] E. Lind et al., IEEE J. El. Dev. Soc. 3, 96 (2015); J. Wallentin et al., Science 339, 1057 (2013).
[2] M. Hjort et al., ACS Nano 6, 9679 (2012); J. Knutsson et al., ACS Appl. Mat. & Interf. 7, 5748 (2015).
[3] M. Hjort et al., Nano Lett. 13, 4492 (2013); M. Hjort et al., ACS Nano 8, 12346 (2014).
[4] O. Persson et al., Nano Lett. 15, 3684 (2015); J. L. Webb et al., Nano Res. 7, 877 (2014).