Polarization-selective, tailorable, and flexible InP nanofilm UV photodetectors

Abstract

Ultraviolet photodetection is critical in many applications such as personal exposure monitoring and visible-blind imaging. In this work, III–V semiconductor nanofilms are demonstrated as an efficient and cost-effective solution with several tailorable properties. By varying the nanofilm thickness from 5 to 550 nm, the transmittance can be varied from near zero up to >50%, photoluminescence peak from ∼870 nm to ∼930 nm (by ∼100 meV), dark current by a factor of 10⁸, and on/off ratio by a factor of 10⁴. The highest responsivities are observed in the thickest films, whereas the 25 nm thick nanofilm has the highest detectivity. The nanofilms exhibit a high UV-to-visible detection ratio and a fast response speed of <1 µs. In polarization-selective detection, an average dichroic ratio of ∼4 is achieved over UV-A wavelengths due to different coupling strengths of the orthogonal polarization states. Finally, the nanofilms show excellent flexibility down to a 2 mm bending radius.