Preferential alignment of Er–2O centers in GaAs:Er,O revealed by anisotropic host-excited photoluminescence

Abstract

When GaAs is co-doped with Er and O by metalorganic chemical vapor deposition, the host-excited photoluminescence (PL) is dominated by 4I13/2→4I15/2 intra-4f-shell luminescence (1.54 μm) from a center identified as an Er atom substituting for Ga, coupled with two O atoms (Er–2O). The preferential alignment of the Er–2O center is revealed by the optical anisotropy exhibited by such samples when detecting host-excited PL polarized parallel to the 〈110〉 crystallographic directions. The preferential alignment of a specific symmetry axis of the Er–2O center is determined to be along the growth direction, [001]. This observation contrasts previous work on rare-earth (RE) doped materials where the RE luminescence center itself exhibits anisotropic luminescent properties, but a random distribution of differently oriented centers results in isotropic host excited PL.