Local structure of 1.54‐μm‐luminescence Er3+ implanted in Si

Extended x‐ray absorption fine structure measurements from Er‐implanted Czochralski‐grown Si samples, which exhibit strong luminescence at 1.54 μm, reveal a local sixfold coordination around Er−not of Si−but of oxygen atoms at an average distance of 2.25 A. By contrast, similar concentrations of Er implanted in high purity float‐zone Si samples, which are essentially optically inactive, show that Er is coordinated to 12 Si atoms at a mean distance of 3.00 A.