Redistribution of chromium under annealed sulfur implants into chromium-doped GaAs

The effect of sulfur implant fluence, ion energy, and annealing temperature on the redistribution accumulation of chromium during annealing of GaAs under SiO2 and Si3N4 caps and a capless condition is shown. The variation of the thickness of the heavily damaged or ‘‘amorphized’’ layer with implant fluence is shown and discussed. Three peaks are seen in the Cr accumulation profiles. When their integrated densities are plotted versus inverse annealing temperature, two peaks exhibit an activation energy for breakup of the Cr-defect complexes of 0.56 eV, and the third, of 1.8 eV. The nature or origin of these Cr-defect complexes is discussed. Sulfur migration or ‘‘diffusion’’ versus sulfur density is illustrated and discussed. The correlations of the two Cr peaks observed in 840 °C annealed depth distributions with capping environment and damage depth are discussed. Finally, these Cr accumulation profiles under sulfur implants are compared with those in self-amorphized GaAs.