LATTICE LOCATION OF ER IN GAAS AND AL0.5GA0.5AS LAYERS GROWN BY MBE ON (100) GAAS SUBSTRATES

The lattice site location of Er in semiconducting materials received c onsiderable interest because its 4I13/2-4I15/2 intra-4f shell luminesc ence, occurring at a wavelength of 1.54 mum, falls in the minimum abso rption window for silica-based fibers. In the present work, results of a study of the lattice location of Er in GaAs:Er and Al0.5Ga0.5As:Er using the Rutherford backscattering/channeling method are presented. T he GaAs:Er and Al0.5Ga0.5As:Er layers were approximately 1.6 mum thick and were grown by conventional elemental source molecular beam epitax y on (100) GaAs substrates. These samples, with Er concentrations of t he order of 10(19) to 10(20) cm-3, presented intense photoluminescence . The RBS/channeling results show that Er atoms are located in the tet rahedral interstitial site in GaAs: Er, and about 70% of the Er atoms are slightly displaced from that site in Al0.5Ga0.5As:Er, the rest bei ng in substitutional sites. For comparison an epitaxial Al0.5Ga0.5As:E r layer with Er concentration of the order of 10(18) cm-3 which does n ot show photoluminescence has been analysed. In this case there is cle ar evidence that Er is substitutionally located.