Depth distribution of carrier lifetime in 65 MeV oxygen ion irradiated silicon wafers

CZ-grown, n-doped crystalline Si(1 1 1) of resistivity 60 Ω cm and 140 Ω cm were irradiated with 65 MeV energy oxygen ions, in the fluence range of 2 x 101-1014 ions/cm2. The depth and spatial profile of excess minority carrier recombination time τ (lifetime) was measured using photoconductive decay (PCD) method. Lifetime measurements were carried out before the stopping range of impinging ions. Results show a monotonous decrease in lifetime with fluence, which is attributed to defect creation mechanism by electronic energy loss based on the thermal spike model. Also, surface modification is expected with a small loss in crystalline quality. This surface is considered to be a multi-crystalline surface with large grain boundaries that act as trapping sites for excess holes in n-Si(1 1 1). Annealing of the irradiated samples showed a near complete recovery at 750 deg. C for a period of 1 h