The talk will focus on the crystal structure and electronic band structure of InAs and InSb-based polytype nanowires (NWs). Typically, bulk form of III-V non-nitride semiconductors exists in the zinc-blende (ZB) phase. However, the NWs of these systems can be fabricated in ZB or in wurtzite (WZ) or in the mixed phase, by varying the growth conditions. The unique crystal structure of the NWs make them potential candidates for future technologies.

InAs NWs on InAs (111)B substrates were grown by chemical beam epitaxy technique. By varying the group III/V flux ratio, the fraction of WZ and ZB crystal phases along their length was tuned [1]. Resonance Raman spectroscopy and density functional theory have been exploited to study the reflection of structural identities of InAs polytype NWs on their electronic band structure [2,3]. We highlight the effect of interfacial strain on the band alignment. We have compared wavelength-dependent polarization anisotropy in bare InAs and InAs/GaSb core-shell NWs and demonstrated the role of NW geometry and to the difference in wavelength dependence of the dielectric constants of core and shell materials in the observed behavior [4]. 

To the end I will discuss the mapping of the electronic band gap along the axis of individual InAs/InSb_xAs_1−x heterostructured  NWs [5]. We demonstrate the fascinating graded band gap in III–V NWs, which, we believe, will find potential applications in the fabrication of optoelectronic devices such as nanoscale multi-terminal photo detectors.

Anushree Roy is a Professor of Physics at the Indian Institute of Technology Kharagpur in India.  After  receiving her PhD degree from Indian Institute of Science, Bangalore in India in the year 1995, Anushree did her post-doctoral studies in University of Tsukuba, Japan; Ecole Polytecnique, Palasau, France and then in University of California, Riverside, USA. She joined IIT Kharagpur in the year 1999. She finds interest in experimental physics, in general.  In condensed matter physics, she is interested in phonon dynamics in solids, primarily using Raman spectroscopic technique.