Unusual features in trap emission characteristics of heavily damaged silicon induced by MeV ion implantation

We have investigated the electrical characteristics of defects in heavily d amaged silicon induced by MeV ion implantation at high doses, by extending the scope of depletion layer capacitance transient techniques. The heavily damaged layer is embedded in the depletion layer of a Schottky diode and hi gh-frequency capacitance measurements are carried out to evaluate charge re laxation kinetics of defects specific to high-dose implantation. Deep-level transient spectroscopy of as-implanted silicon shows presence of the divac ancy trap (V-2) and relatively high concentration of a damage-related trap (D1) with unusual spectral lineshape. Thermally stimulated capacitance spec tra show large capacitance step even without application of a trap-filling pulse. Constant-capacitance time-analysed transient spectroscopy studies of the D1 peak reveal that the skewed peakshape is due to premature terminati on of the transient signal during trap emission. Strong temperature depende nce of spectral lineshape, ranging from broad to narrow peak (stronger than that expected from exponential transient), and trap occupancy points to a dynamic interdependence of trap occupancy and quasi-Fermi level. Unusual fe atures in spectral lineshape are simulated by introducing a time-dependent capture term into the rate equations for trapping dynamics for a single tra p level and provide strong support for our model on the dynamic interdepend ence of quasi-Fermi level and trap occupancy. The defect parameter is found to be sensitive to implantation dose and low-temperature annealing. The D1 trap is ascribed to small self-interstitial clusters.