SnSe Nanoplates for Photodetectors with a High Signal/Noise Ratio

In this work, we report a study on two-dimensional SnSe nanoplates grown by chemical vapor deposition and their applications in single nanoplate photodetectors with a high signal/noise ratio. The SnSe nanoplates present a square shape with a lateral size (side length) up to ∼8 μm. The lateral dimension of SnSe nanoplates increases with increasing the growth temperature from 400 to 440 °C and then saturates with increasing the growth temperature further due to the competition between SnSe molecules transported and those consumed on the surface of the substrate. The SnSe nanoplate photodetectors fabricated show excellent device performance at room temperature with a responsivity of 1.32 A/W, a specific detectivity of 1.01 × 1011 Jones, an external quantum efficiency of 408.37%, and a response time (trising/treset) of 0.24/0.15 s under 1 V bias and 400 nm laser illumination. More importantly, the SnSe nanoplate photodetector exhibits a dark current of 130 pA, a low white noise of 4.8 × 10–15 A/Hz1/2, and a high photo-switching ratio up to 176.14, which is the highest value reported so far for a SnSe photodetector. The low-level dark current and white noise indicate a high signal-to-noise ratio for the SnSe nanoplate detector device. These detector performance parameters imply the great promise of SnSe nanoplates for applications in making photodetectors with low noise and a high signal/noise ratio.