Open AccessTunable absorption resonances in the ultraviolet for InP nanowire arrays
Author(s) -
Mahtab Aghaeipour,
Nicklas Anttu,
Gustav Nylund,
Lars Samuelson,
Sebastian Lehmann,
Mats Erik Pistol
Publication year - 2014
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.22.029204
Subject(s) - materials science , nanowire , refractive index , wurtzite crystal structure , optoelectronics , optics , absorption (acoustics) , ultraviolet , absorptance , crystal (programming language) , photodetector , spectral line , dispersion (optics) , blueshift , wavelength , phase (matter) , photoluminescence , reflectivity , chemistry , zinc , physics , organic chemistry , astronomy , computer science , metallurgy , composite material , programming language
The ability to tune the photon absorptance spectrum is an attracting way of tailoring the response of devices like photodetectors and solar cells. Here, we measure the reflectance spectra of InP substrates patterned with arrays of vertically standing InP nanowires. Using the reflectance spectra, we calculate and analyze the corresponding absorptance spectra of the nanowires. We show that we can tune absorption resonances for the nanowire arrays into the ultraviolet by decreasing the diameter of the nanowires. When we compare our measurements with electromagnetic modeling, we generally find good agreement. Interestingly, the remaining differences between modeled and measured spectra are attributed to a crystal-phase dependence in the refractive index of InP. Specifically, we find indication of significant differences in the refractive index between the modeled zinc-blende InP nanowires and the measured wurtzite InP nanowires in the ultraviolet. We believe that such crystal-phase dependent differences in the refractive index affect the possibility to excite optical resonances in the large wavelength range of 345 < λ < 390 nm. To support this claim, we investigated how resonances in nanostructures can be shifted in wavelength by geometrical tuning. We find that dispersion in the refractive index can dominate over geometrical tuning and stop the possibility for such shifting. Our results open the door for using crystal-phase engineering to optimize the absorption in InP nanowire-based solar cells and photodetectors.