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

Abstract

We have investigated the electrical characteristics of defects in heavily damaged 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 high-frequency capacitance measurements are carried out to evaluate charge relaxation kinetics of defects specific to high-dose implantation. Deep-level transient spectroscopy of as-implanted silicon shows presence of the divacancy trap (V 2 ) and relatively high concentration of a damage-related trap (D1) with unusual spectral lineshape. Thermally stimulated capacitance spectra 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 termination of the transient signal during trap emission. Strong temperature dependence 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 features in spectral lineshape are simulated by introducing a time-dependent capture term into the rate equations for trapping dynamics for a single trap level and provide strong support for our model on the dynamic interdependence 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.

Deep-level transient spectroscopy of low-energy ion-irradiated silicon

“…10,11 They have formulated a general model of charge transfer among coupled defect states in semiconductors, where the freecarrier density is limited by the density of unoccupied trap levels, and shown, that this model in the special case of the divacancy level in Si, can explain the observed slowing down of the filling time from a few tens of nanoseconds in the low-defect case to the millisecond scale in the case of heavy damage.…”

Electrical properties of hydrogen‐implanted Si annealed under high hydrostatic pressure

“…Recently, the latter together with X-ray Reciprocal Space Mapping (XRSM), and photoluminescence measurements (PL) have been used to study the evolution of post-implant defects due to heat treatment under high hydrostatic pressure [3]. An increasing interest has been observed in using electrical methods for the characterisation of defects induced in the region heavily damaged by ion-implantation [4,5].…”