Excitation mechanisms and structure-related Er3+ emission in amorphous andnanocrystalline GaN films

We report on Er3+ luminescence at room temperature in the visible and infra red regions in amorphous GaN:Er films prepared by DC magnetron co-sputterin g. The intensity of the Er3+ luminescence at 1535 nm corresponding to the I -4(13/2) --> I-4(15/2) transition increased after annealing at 750 degreesC . During annealing GaN crystallites form in the amorphous matrix. The cryst allite diameters are between 4 and 7 nm as analyzed by high-resolution tran smission electron microscopy (HRTEM). A shallow exponential absorption edge extends three orders of magnitude in absorption coefficient over the spect ral range from 0.5 to 3.5 eV. On this exponential absorption are superimpos ed the resonant absorption bands of Er3+ ions. (C) 2001 Elsevier Science B. V. All rights reserved.