InSb nanowires for multispectral infrared detection

InSb nanowire (NW) arrays fabricated by a top-down etching process were investigated for multispectral infrared photodetection. A 2.5 μm thick film of InSb was grown on Si (100) by molecular beam epitaxy using an AlSb buffer layer to alleviate defects associated with lattice mismatch strain, as confirmed by scanning electron microscopy and x-ray diffraction. Using a Ti mask patterned by electron beam lithography, InSb NW arrays with diameters ranging from 300 to 1300 nm (100 nm steps) and pitches ranging from 1000 nm to 3500 (500 nm steps) were reactive ion etched from the thin film. For each 100 nm increase in NW diameter, the peak absorptance wavelength, as measured by Fourier transform infrared spectroscopy, increased by 0.53 ± 0.2 μm. The ability of InSb nanowires to produce highly tunable absorptance from 1.61 to 6.86 μm was demonstrated.