ELECTRON-PARAMAGNETIC-RESONANCE EVIDENCE FOR REVERSIBLE TRANSFORMATION OF THERMAL DONOR INTO SHALLOW DONOR-TYPE CENTER IN HYDROGEN-IMPLANTED SILICON

Electron paramagnetic resonance spectrum of the proton-related thermal donor (TD) assigned as NL8 paramagnetic center has been detected at 1 10 K after heat treatment of the hydrogen-implanted Czochralski-Si at 773 K. The effect of temperature on reversible transformations of the anisotropic spectrum of NL8 center into the isotropic singlet line was studied in the temperature region from 110 to 240 K. The analysis of the singlet provides an evidence that this signal originates from the proton- related shallow donor type at g = 1.9987. The changes in the l inewidth have been used to evaluate the parameters [1/tau = 0.66 x 10( 12) exp(-Delta E/kT); Delta E = 169 meV] for thermally activated elect ron emission to the conduction band from the second donor state of the NL8 center. These results represent direct experimental evidence of r eversible transformation of the TD+ charged center into the shallow do nor-type center. (C) 1998 American Institute of Physics. [S0003-6951(9 8)01548-4].