Photoluminescence in pulsed-laser deposited GeGaSbS:Er films

The complex dielectric function, the Er³⁺ Stokes emission at ≈1540 nm and the upconversion photoluminescence at ≈990 nm of pulsed-laser deposited thin-film GeGaSbS:Er³⁺ were studied. The film shows ≈990 nm upconversion photoluminescence originating from the E^r3+: ⁴I_11/2→⁴I_15/2 transition under a 1550 nm excitation. The compositional trends of the photoluminescence intensity are attributed to the presence of Er clusters which may lead to unfavorable concentrationquenching, radiation-trapping and reabsorption processes in the sulphur deficient films.