Multispectral absorptance from large-diameter InAsSb nanowire arrays in a single epitaxial growth on silicon

Vertical III-V nanowires are capable of resonant absorption at specificwavelengths by tuning the nanowire diameter, thereby exceeding the absorption of equivalent thinfilms. These propertiesmay be exploited to fabricatemultispectral infrared (IR) photodetectors, directly integratedwith Si, without the need for spectral filters or vertical stacking of heterostructures as required in thinfilm devices. In this study,multiple InAsSb nanowire arrays were grown simultaneously on Si bymolecular beam epitaxywith nanowire diameter controlled by the nanowire period (spacing between nanowires). This is thefirst such study of patterned InAsSb nanowires where control of nanowire diameter andmultispectral absorption are demonstrated. The antimony fluxwas used to control axial and radial growth rates using a selective-area catalyst-free growthmethod, achieving large diameters, spanning 440–520 nm,which are necessary for optimum IR absorption. Fourier transform IR spectroscopy revealed IR absorptance peaks due to theHE11 resonance of the nanowire arrays in agreementwith optical simulations. Due to the dependence of theHE11 resonance absorption on nanowire diameter,multispectral absorptionwas demonstrated in a singlematerial system and a single epitaxial growth stepwithout the need for bandgap tuning. This work demonstrates the potential of InAsSb nanowires formultispectral photodetectors and sensor arrays in the shortwavelength IR region.