Photoreflectance of GaSb/Al0.4Ga0.6Sb single quantum wells

We report a photoreflectance study conducted in the 0.7–1.2 eV photon energy range and at temperatures from 80 to 300 K of GaSb/Al0.4Ga0.6Sb single quantum wells grown by molecular beam epitaxy. We observed clear and well-resolved structures, which could be attributed to the interband optical transitions originating in both the GaSb buffer and the quantum wells, and which could be fitted by standard critical-point line shapes. Our results demonstrate that even unintentionally doped GaSb-based quantum systems can be studied and characterized by photoreflectance, especially at low temperatures

Luminescence from beta-FeSi_2 Precipitates in Si. II: Origin and Nature of the Photoluminescence

In this paper we present photoluminescence, photoreflectance, and absorbance measurements on silicon samples with b-FeSi2 precipitates, as structurally characterized in the first part of this paper @M. G. Grimaldi et al., Phys. Rev. B 66, 085319 (2002). By comparing the photoluminescence measurements in different experimental conditions and with excitation energy above and below the silicon threshold, by considering the direct gap estimations by photoreflectance and absorption, we argue that the 1.54 mm photoluminescence peak in the spectra is produced by an indirect transition in the disc-shaped precipitates. However, the latter ones are predicted to be the most efficient configuration, acting as a trapping well for carriers generated in the silicon matrix, and displaying a high structural quality with no dangling bonds at the b-FeSi2 /Si interface. Our simple model, based on band lineup at the interface, is also able to explain the temperature quenching of the photoluminescence peak