Electrically tunable spectral response in vertical nanowire arrays

Abstract

The semiconductor nanowire (NW) array promises a high photoconductive-gain as well as an enhanced light-absorption in optoelectronic applications. However, to date, the two kinds of advantages are always consuming each other, leading to a low global income. In this work, we show a feasible route to balance the electric gain and the light absorption efficiency. It is accomplished by an inverse injection of photocarriers into NW (from the tip to the bottom of NW or in the opposite direction), which will activate the photoconductive gain in maximal degree. Experimentally, the responsivity reaches up to ∼200 A/W. The spectral response of the GaAs nanowire-array detector is proven to be bias-voltage controlled, allowing it to work at visible or shortwave-infrared enhanced modes. Also, the photoresponse carries on the wavelength information of the incident light, thus, can be used to discriminate monochromatic lights from each other. Together, these findings depict a full image of the photoresponse process in the vertical nanowire array. It might pave a way for the design and fabrication of subwavelength optoelectronic devices.