Engineering light absorption in semiconductor nanowire devices

Quantum confinement effects have an important role in photonic devices. However, rather than seeking perfect confinement of light, leaky-mode resonances are shown to be ideally suited for enhancing and spectrally engineering light absorption in nanoscale photonic structures. 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.