High-performance multicolor p-Ag:NiOx/n-Si heterojunction photodiode enhanced by Ag-doped NiOx

Abstract

Silver (Ag)-doped NiOx (Ag:NiOx) is employed to enhance the broad-band spectrum from ultraviolet (UV) and visible to infrared response of multicolor p-NiOx/n-Si heterojunction photodiodes (HPDs). The Ag:NiOx is spin coated on n-Si substrate with a molar ratio (AgNO3:Ni(CH3COO)2) of 1.6:1. In comparison with conventional p-NiOx/n-Si HPDs, p-Ag:NiOx/n-Si HPDs significantly increase the rectification ratio from 5.7 × 102 to 3.4 × 104 (60 times). The Ag-doped NiOx largely enhance the photoresponse of the prepared HPDs in the wavelength range of 300–1000 nm. The enhancement factor exceeds 100 times for the wavelength longer than 500 nm, and reaches a maximum (213 times) at 900 nm. The Ag-doped NiOx increases photo-to-dark current ratio in the prepared HPDs, the ratio is enhanced by about 180 times in the visible and infrared light. The mechanism is caused by that the conductivity of Ag-doped NiOx is increased owing to the inducing crystallization of NiOx by Ag atoms. The Ag atoms accumulate at the grain boundaries of Ag:NiOx nanoclusters and passivate the point defects of Ag:NiOx. The Ag atoms in Ag:NiOx diffuse into the n-Si and convert the top surface of n-Si into p-Si. The graded potential in p-Si and built-in field at p-Si/n-Si interface accelerate the photo-generated carriers to be extracted, leading to a higher broad-band phtotoresponse.