Ab initio study of electronic structures of InAs and GaSb nanowires along various crystallographic orientations |
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| Affiliation: | 1. Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210, USA;2. Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA;1. School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland;2. Tyndall National Institute, University College Cork, Lee Maltings, Cork, Ireland;3. National Institute of Standards and Technology, Gaithesburg, MD 20899, USA;4. U.S. Army Research Laboratory, Adelphi, MD 20783, USA;1. Lviv Polytechnic National University, S. Bandera Str. 12, 79013 Lviv, Ukraine;2. Institute of Low Temperature and Structure Research PAS, Gajowicka Str., 95, Wroclaw, Poland;1. School of Electrical, Electronic & Computer Eng., The University of Western Australia, Crawley, WA 6009, Australia;2. Dept. of Electrical Engineering, Yale University, New Haven, 06511 CT, USA;3. IMEP-LAHC, Grenoble INP Minatec, BP 257, 38016 Grenoble, France;1. School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471003, People''s Republic of China;2. State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012, People''s Republic of China;3. School of Electric and information Engineer, Zhongyuan University of Technology, Zhongyuan Road 41, Zhengzhou 450007, People''s Republic of China;1. Functional Nanomaterials Research Laboratory, Department of Applied Physics, Indian Institute of Technology (ISM), Dhanbad 826004, India;2. Department of Applied Chemistry, Indian Institute of Technology (ISM), Dhanbad, India |
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| Abstract: | InAs and GaSb nanowires oriented along different crystallographic axes—the [0 0 1], [1 0 1] and [1 1 1] directions of zinc-blende structure—have been studied utilizing a first-principles derived nonlocal screened atomic pseudopotential theory, to investigate the band structure, polarization ratio and effective masses of these semiconductor nanowires and their dependences on the wire lateral size and axis orientation. The band energy dispersion over entire Brillouin zone and orbital energy are determined and found to exhibit different characteristics for three types of wires. There is an explicit dispersion hump in the conduction bands of [0 0 1] nanowires with two larger diameters and [1 0 1] nanowires with the smallest diameter considered. Moreover, the [1 1 1] nanowires are shown to exhibit very different orbital energy for the maximum valence state at the zone-boundary point, compared with [0 0 1] and [1 0 1] nanowires. These differences present significant and detailed insight for experimental determination of the band structure in InAs and GaSb nanowires. Furthermore, we study the polarization ratio of these nanowires for different orientations. Our calculation results indicate that, for the same lateral size, the [1 1 1] nanowires give extraordinarily higher polarization ratio compared to nanowires along the other two directions, and at the same time have larger band-edge photoluminescence transition intensity. Consequently, the [1 1 1] nanowires are predicted to be better suitable for optoelectronic applications. We also significantly find that polarization ratio and transition intensity displays different varying trend of dependence on lateral size of nanowires. Specially, the calculated polarization ratio is shown to increase with the decreasing size, which is opposite to the behavior displayed by the optical transition intensity. The predicted polarization ratios of [1 0 1] and [1 1 1] nanowires for 10.6 Å diameter approach the limit of 100%. In addition, the electron and hole masses for InAs and GaSb nanowires with different crystallographic axes have been calculated. For the [1 0 1] and [1 1 1] oriented nanowires, the hole masses are predicted to be around 0.1–0.2 m0, which are notably smaller than the values (∼0.5 m0) along the same direction for their bulk counterparts. Thus, we demonstrates an inspired possibility of obtaining a high hole mobility in nanowires that is not available in bulk. The small hole mobility is interpreted as to be associated with the strong electronic band mixing in nanowires. |
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