Construction Of ZnSe Nanowires/Black Si Heterojunction And Its Optoelectronic Applications

Black silicon is a kind of surface treated silicon material, compared with the ordinary silicon the most prominent advantage is super high absorption rate, the black silicon in visible light band absorption rate can reach more than 80%. ZnSe is a kind of important II-VI wide bandgap semiconductor, and the forbidden band width is 2.7 eV at room temperature. It has important applications in photodetector and photovoltaic devices. Nano heterojunction is the basic part of nanoscale optoelectronic devices, so the construction of black silicon and ZnSe heterojunction and improve its performance has important research significance. In this study, we report the fabrication of ZnSeNWs/Black Si p-n heterojunction arrays by directly growing the p-type ZnSeNWs on the black silicon substrate for optoelectronic device application, results are mainly as follows:1. Micron-sized pyramids spread over the whole Si wafer closely packed and morphology by using the method of auxiliary metal etching and the side length of the pyramid is about 5-8μm, on the surface of the pyramids the nanometer column can reach about 300 run, the black silicon in visible light absorption rate can reach more than 95%.2. Sb was used as dopant to achieve robust p-type doping in the ZnSe nanostructures via chemical vapor deposition (CVD) method. The result reveals that the ZnSe:Sb nanowires are clean and uniform.3. Photoelectric devices based on the heterojunction arrays were then constructed through directly transferring the multi-layer graphene film onto the top of the ZnSeNWs as the transparent electrode. Devices showed a large fill factor (FF) of ～25%, yielding a power conversion efficiency of ～1.06%. Moreover, thanks to the matched bandgap and the light trapping arising from the black silicon substrate, the heterojunction arrays exhibited improved light absorption, particularly in the blue/UV wavelength range. The device exhibits pronounced a fast response speed, excellent selectivity, and good reproducibility behavior to 450 nm illumination under zero bias with a wide range of switching frequencies (1 kHz-100 kHz). What is more, the device shows small noise currents which are the key to achieving such small NEP values for the photodetectors. It suggests that ZnSeNWs/Black Si p-n heterojunction will have potential application in future optoelectronic devices.4. The black silicon with AgNPs decorated and the vertical silicon nanowires array prepared using Ag-assisted chemical etching approach were constructed as devices with grapheme helped. Because of the SPR effect and light trapping, the devices have a excellent performance.