Epitaxial Er-doped GaAs and Al0.5Ga0.5As films, 1.6 μm thick, grown by MBE on (100) GaAs substrates at 560°C, with Er concentrations in the range 9 × 1017 to 2 × 1020 cm−3 were studied with RBS/channeling and photoluminescence techniques. Angular scans in the <110> and <111> axial and (111) planar directions indicate that the Er atoms in GaAs are located on interstitial sites. In Al0.5Ga0.5As doped with 5 × 1019 Er cm−3, 70% of the Er atoms are on positions slightly displaced from the interstitial site, the rest presumably substitutional. In Al0.5Ga0.5As doped with 9 × 19 Er cm−3, more than 88% of the Er atoms are on substitutional sites.
Photoluminescence around 1.54 μm is observed at room-temperature in Er-doped Al0.5Ga0.5As. Both the low and highly Er-doped samples show similar luminescence intensities; the luminescence lifetimes are on the order of 1 ms. The Er-doped GaAs does not show any measurable signal at room-temperature. Correlation of the luminescence data to the Er lattice location suggests that only substitutional Er in AlGaAs is in the luminescent trivalent state.