Photoinduced carrier annihilation in silicon pn junction

Abstract

We report analysis of the photo-induced minority carrier effective lifetime (τeff) in a p+n junction formed on the top surfaces of a n-type silicon substrate by ion implantation of boron and phosphorus atoms at the top and bottom surfaces followed by activation by microwave heating. Bias voltages were applied to the p+ boron-doped surface with n+ phosphorus-doped surface kept at 0 V. The values of τeff were lower than 1 × 10−5 s under the reverse-bias condition. On the other hand, τeff markedly increased to 1.4 × 10−4 s as the forward-bias voltage increased to 0.7 V and then it leveled off when continuous-wave 635 nm light was illuminated at 0.74 mW/cm2 on the p+ surface. The carrier annihilation velocity at the p+ surface region was numerically estimated from the experimental τeff. ranged from 4000 to 7200 cm/s under the reverse-bias condition when the carrier annihilation velocity at the n+ surface region was assumed to be a constant value of 100 cm/s. markedly decreased to 265 cm/s as the forward-bias voltage increased to 0.7 V.