High responsivity MSM black silicon photodetector

The effect of annealing temperature on photoelectric properties of metal–semiconductor–metal (MSM) black silicon photodetector has been studied. The black silicon was fabricated by alkaline etching and metal assisted etching. The nanopores and micro-columns formed by the etching process enhance spectral absorptance significantly at wavelength from 250 nm to 1100 nm. The MSM black silicon photodetectors were annealed at different temperatures in N₂ ambient with a rapid thermal annealing (RTA) process. The fast ramp-up and cool-down rate of RTA is a key factor that eliminates the tensile stress and point defects in Si nanoparticle made from metal assisted wet etching, leading to significant increase of mobility, conductivity and carrier concentration. In addition, the photocurrent and spectral responsivities of detectors increase with annealing temperature. At the wavelength of 600 nm, the responsivity (76.8 A/W) at 673 K is almost three orders of magnitude greater than that of the unannealed sample.