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 considerable interest because its 4I13/2-4I15/2 intra-4f shell luminescence, occurring at a wavelength of 1.54 mum, falls in the minimum absorption 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. The GaAs:Er and Al0.5Ga0.5As:Er layers were approximately 1.6 mum thick and were grown by conventional elemental source molecular beam epitaxy on (100) GaAs substrates. These samples, with Er concentrations of the order of 10(19) to 10(20) cm-3, presented intense photoluminescence. The RBS/channeling results show that Er atoms are located in the tetrahedral 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 being in substitutional sites. For comparison an epitaxial Al0.5Ga0.5As:Er layer with Er concentration of the order of 10(18) cm-3 which does not show photoluminescence has been analysed. In this case there is clear evidence that Er is substitutionally located.