Defect accumulation during ion irradiation of crystalline Si probed by in situ conductivity measurements

Abstract

We have used in situ conductivity measurements to investigate the defect evolution and accumulation in ion implanted crystalline Si. Upon irradiation at room temperature with 400 keV Si ions the initial conductivity (4×10−2 Ω−1 cm−1) decreases by about 4 orders of magnitude to a value of 2×10−6 Ω−1 cm−1, characteristic of intrinsic silicon, at a fluence of 1×1013/cm2 and then slowly increases at higher fluences. Deep level transient spectroscopy measurements, transmission electron microscopy analyses, and thermal annealings were performed on samples irradiated at various fluences. The data demonstrate that the strong conductivity decrease at low fluences is the result of a dopant compensation produced by deep levels introduced by divacancies and complex defects in the band gap. At higher fluences the conduction is dominated by electron hopping in a buried continuous amorphous layer produced by irradiation. These results are reported and discussed.