Thermal donors formation via isothermal annealing in magnetic Czochralski high resistivity silicon

Abstract

A quantitative study about the thermal activation of oxygen related thermal donors in high resistivity p -type magnetic Czochralski silicon has been carried out. Thermal donor formation has been performed through isothermal annealing at 430 °C up to a total time of 120 min. Space charge density after each annealing step has been measured by transient current technique. The localized energy levels related to thermal double donors (TD) have been observed and studied in details by thermally stimulated currents (TSCs) in the range of 10-70 K, and activation energies E and effective cross sections σ have been determined for both the emissions TD0+ (E=75±5 meV, σ=4× 10-14 cm2) and TD++ (E=170±5 meV, σ=2× 10 -12cm 2). The evolution of the space charge density caused by annealing has been unambiguously related to the activation of TDs by means of current deep level transient spectroscopy TSC, and current transients at constant temperature i (t,T). Our results show that TDs compensate the initial boron doping, eventually provoking the sign inversion of the space charge density. TD's generation rate has been found to be linear with the annealing time and to depend critically on the initial interstitial oxygen concentration, in agreement with previous models developed on low resistivity silicon. © 2006 American Institute of Physics.