Low temperature scanning tunneling microscopy and spectroscopy on laterally grown In_xCa_(1-x)As nanowire devices

摘要

Laterally grown In_xGa_(1-x)As nanowires (NWs) are promising candidates for radio frequency and quantum computing applications, which, however, can require atomic scale surface and interface control. This is challenging to obtain, not least due to ambient air exposure between fabrication steps, which induces surface oxidation. The geometric and electronic surface structures of In_xGa_(1-x)As NWs and contacts, which were grown directly in a planar configuration, exposed to air, and then subsequently cleaned using atomic hydrogen, are studied using low-temperature scanning tunneling microscopy and spectroscopy (STM/S). Atomically flat facets with a root mean square roughness of 0.12 nm and the InGaAs (001) 4 × 2 surface reconstruction are observed on the top facet of the NWs and the contacts. STS shows a surface bandgap variation of 30 meV from the middle to the end of the NWs, which is attributed to a compositional variation of the In/Ga element concentration. The well-defined facets and small bandgap variations found after area selective growth and atomic hydrogen cleaning are a good starting point for achieving high-quality interfaces during further processing.