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

Abstract

Vertical III-V nanowires are capable of resonant absorption at specific wavelengths by tuning the nanowire diameter, thereby exceeding the absorption of equivalent thin films. These properties may be exploited to fabricate multispectral infrared (IR) photodetectors, directly integrated with Si, without the need for spectral filters or vertical stacking of heterostructures as required in thin film devices. In this study, multiple InAsSb nanowire arrays were grown simultaneously on Si by molecular beam epitaxy with nanowire diameter controlled by the nanowire period (spacing between nanowires). This is the first such study of patterned InAsSb nanowires where control of nanowire diameter and multispectral absorption are demonstrated. The antimony flux was used to control axial and radial growth rates using a selective-area catalyst-free growth method, achieving large diameters, spanning 440–520 nm, which are necessary for optimum IR absorption. Fourier transform IR spectroscopy revealed IR absorptance peaks due to the HE11 resonance of the nanowire arrays in agreement with optical simulations. Due to the dependence of the HE11 resonance absorption on nanowire diameter, multispectral absorption was demonstrated in a single material system and a single epitaxial growth step without the need for bandgap tuning. This work demonstrates the potential of InAsSb nanowires for multispectral photodetectors and sensor arrays in the short-wavelength IR region.

Growth of Self-Catalyzed InAs/InSb Axial Heterostructured Nanowires: Experiment and Theory

“…Instead, InSb starts forming a shell around the InAs stem (see the Supplementary material). We can thus conclude that axial growth of InSb on InAs can only proceed in the presence of an In droplet through the VLS growth mode, while no axial growth occurs in the catalyst-free VS regime, as observed earlier in [14,15]. Figure 2b shows the diameter and length of InSb segment as a function of F Sb .…”

“…Furthermore, the top InSb segment rapidly widens with respect to InAs stem [6][7][8][9][10][11][12][13]. Similar effect is observed for ternary InAsSb segments [14,15]. This radial extension of the InSb segment can be caused by several reasons, such as the droplet inflation with either In or Sb atoms, or a rapid radial growth on…”

Evolution of the Length and Radius of Catalyst-Free III–V Nanowires Grown by Selective Area Epitaxy

“…The NW length increases superlinearly with time until it reaches the diffusion length of 1000 nm, after which the time evolution of length becomes sublinear. The further increase of ε up to its maximum value of 2/3 may lead to situations where the NW radius increases faster than the length so that NWs become nanodiscs, as in ref (5) for InAsSb NWs grown on InAs stems.…”

Circular Polarization Discrimination Enhanced by Anisotropic Media

“…Concerning a typical nanowire diameter of 40–80 nm and an averaged inter‐distance of 110–220 nm, the fill factor, which is defined as the ratio of the nanowire cross‐section area to the pitch size, is evaluated to be ≈10%. Since both the lateral size and the separation of the nanowires are much smaller than mid‐infrared wavelengths, even when taking into account the refractive index of InAsSb (≈3.8 [ 61–63 ] ) and that of the polymer matrix (≈1.6 [ 50 ] ), the encapsulated nanowire array can be regarded as an effective medium with the diagonal components of the relative permittivity tensor expressed as where f s denotes the fill factor, f e = 1‐ f s , and ε s and ε e represent the relative permittivities of the InAsSb and the matrix, respectively. Equations () and () are based on the Bruggeman formalism derived by Mackay.…”