Annihilation properties of photo-induced carrier in silicon pn junction

We report analysis of the photo-induced minority carrier effective lifetime (τ_eff) in p⁺n junction formed on the top surfaces of n-type silicon substrates by ion implantation of boron and phosphorus atoms at top and bottom surfaces followed by activation by microwave heating. The values of τ_eff were lower than 1×10^-5 s in the reverse bias condition when continuous wave 635 nm light was illuminated at 0.74 mW/cm² to the p⁺ surface. On the other hand, τ_eff markedly increased to 1.4×10^-4 s as the forward bias voltage increased to 0.7 V and then it leveled off above 0.7 V. Numerical analysis indicated that the carrier annihilation velocity at the p⁺ surface region was strongly depended on the bias voltage.