| Si-based NIR photodetectors have attracted considerable research attention due to its excellent compatibility with CMOS technology. There are many kinds of Si-based photodetectors, such as Schottky junction based photodetector, p-n junction based photodetector,and p-i-n junction based photodetector. Among them,Schottky junction based photodetectors have been the prominent one because of their simple device architecture, fast response speed and small parasitic capacitance. In comparison to thin film and bulk materials based photodetectors, devices made from semiconductor nanostructures exhibit obvious advantages such as high sensitivity, low energy consumption and high response speed which may be ascribed to the increased photon collection efficiency arising from their low reflectance and high surface-to-volume ratio and the shorter transit time of the carriers defined by the low dimensions of the effective conductive channel. By this token, one-dimensional (1D) Si nanostructures, in particular Si nanowire NW array with a strong light-trapping effect,have a great potential in the field of high-performance IR photodetectors. In addition, Cu is known to be an important metallization material for microelectronic devices due to its low resistivity and high electromigration resistance. Herein, a core-shell SiNW array/Cu nanofilm Schottky junction NIR photodetector is reported. The detailed results are as follow:1. The controllable growth of Si nanowires array was realized with the method of Ag ion assisted etching on the n-type light doped Si substrate. According to the SEM images, the nano wires array has a uniform length of 4 ?m and average diameter of 150 nm (mostly 100-300 nm).2. A layer of uniform Cu film was deposited onto the surface of Si nanowires array through the hydrothermal reaction in the water/ethylene glycol/hydrazine hydrate mixed system (Cu(NO3)2 as the source of copper,100 0C 30 min),successfully fabricating the core-shell SiNW array/Cu Schottchy junction. HRTEM images and elements Mapping showed that the surface of Si nanowires was evenly coated with about 15 nm Cu film, which is composed of Cu particles with size about 5-10 nm.3. A layer of In/Ga conductive adhesive was brushed to the bottom of Cu/Si core-shell nanowires array structure as the bottom electrode contact. Then the device was fixed by PCB and Cu foil and electrodes for electrical characterization were extracted with silver paste and silver wires. The electrical characterizations show that the as-fabricated core-shell Cu/SiNW array Schottky junction exhibits an obvious rectifying behavior with a turn-on voltage of ?0.4 V and a rectification ratio of about 102 at ±1.5 V bias. In addition,it shows a pronounced photovoltaic performance when illuminated by 0.22 mW cm-2 NIR light with a wavelength of 980 nm (open-circuit voltage VOC 0.3 V, short-circuit current Isc 16.2 mA and photoelectric conversion efficiency ?2.56 %, respectively). The responsivity, detectivity and on-off ratio of the self-power NIR photodetector were estimated to be 0.335 A W-1,2.9×1012 cm Hz1/2 W-1 and 104, respectively. It is revealed that our device has a slow relative balance decay even when the switching frequency reaches 30 kHz. The response time and the recovery time are 3.6 ?s and 14.2 ?s, respectively. |
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