Engineering light absorption in semiconductor nanowire devices


The use of quantum and photon confinement has enabled a true revolution in the development of high-performance semiconductor materials and devices1,2,3. Harnessing these powerful physical effects relies on an ability to design and fashion structures at length scales comparable to the wavelength of electrons (1 nm) or photons (1 μm). Unfortunately, many practical optoelectronic devices exhibit intermediate sizes4,5 where resonant enhancement effects seem to be insignificant. Here, we show that leaky-mode resonances, which can gently confine light within subwavelength, high-refractive-index semiconductor nanostructures, are ideally suited to enhance and spectrally engineer light absorption in this important size regime. This is illustrated with a series of individual germanium nanowire photodetectors. This notion, together with the ever-increasing control over nanostructure synthesis opens up tremendous opportunities for the realization of a wide range of high-performance, nanowire-based optoelectronic devices, including solar cells6,7,8, photodetectors9,10,11,12,13, optical modulators14 and light sources 14,15.

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Figure 1: Measurement of light absorption in individual germanium nanowire devices.
Figure 2: Correlation of the absorption peaks in germanium nanowires with LMR.
Figure 3: Graphs illustrating the tuneability of the absorption efficiency, Qabs, in germanium nanowires.
Figure 4: Polarization dependence of the absorption efficiency, Qabs, and its dependence on nanowire diameter.
Figure 5: Dependence of the absorption efficiency, Qabs, on incident angle.


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We thank M. Preiner, S. Fan, F. Wang and Y. Cui for useful discussion during different stages of this project. This work was sponsored by the Si-based Laser Initiative of the Multidisciplinary University Research Initiative (MURI) under the Air Force Aerospace Research OSR Award Number FA9550-06-1-0470 and supervised by LTC Gernot Pomrenke. L.C. acknowledges the 2008 SPIE scholarship in Optical Science and Engineering. J.-S.P. acknowledges financial support from the System IC 2010 program of the Ministry of Knowledge Economy in the Republic of Korea.

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L.C. and M.L.B conceived the experiments. L.C. and J.-S.P. fabricated the nanostructures. L.C. and J.S.W. carried out the optical experiments. L.C., J.S.W., J.A.S. and M.L.B. analysed the data. All authors were involved in writing the manuscript.

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Correspondence to Mark L. Brongersma.

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Cao, L., White, J., Park, JS. et al. Engineering light absorption in semiconductor nanowire devices. Nature Mater 8, 643–647 (2009).

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