High performance ultraviolet photodetector based on a spray-coated nanocrystal quantum dots layer and Si photodiode

We developed a high performance and wide active area ultraviolet (UV) photodiode from a normal silicon (Si) photodiode (SiPD) and UV-excited nanocrystal quantum dots (QDs). A thickness-controlled QD layer of 0.3-2.7 μm thickness was formed by a simple spraying and drying process to optimize UV detection. As a result, photocurrents 2.2-5.9 times higher than those of a bare SiPD were observed under UV light of 250-400 nm wavelength. The responsivity of the QD-coated SiPD was shown to reach to greater than 300% of the bare SiPD, and 150% of a gallium phosphide (GaP) UV PD. The effects of the thickness of the QD layer and the wavelength of incident light on UV detection were investigated according to the surface morphology analysis, and optical and photoluminescence characteristics of the deposited QD layers. We believe that the proposed technology opens the way to manufacturing cost-effective and high performance UV PDs that can be applied to UV-based chemical and biological sensing.