RESUMO
A new approach to realize ultraviolet (UV) light emitting diodes (LEDs) is using AlN/GaN or AlxGa1-xN/GaN SL structure as active layers. Effect of a uniaxial strain on the degree of polarization (DOP) of Al0.26Ga0.74N/GaN superlattices (SLs) grown on c-plane sapphire substrates has been investigated. Compared with AlN/AlxGa1-xN quantum wells, the DOP of the light emission from Al0.26Ga0.74N/GaN SLs shows an opposite variation tendency with in-plane strain and quantum confinement. The results would be helpful to the structural design of c-plane deep-UV and UVA LEDs to enhance surface emission.
RESUMO
The exciton localization in wurtzite AlxGa1-xN alloys with x varying from 0.41 to 0.63 has been studied by deep-ultraviolet photoluminescence (PL) spectroscopy and picosecond time-resolved PL spectroscopy. Obvious S-shape temperature dependence was observed indicating that the strong exciton localization can be formed in high Al composition AlxGa1-xN alloys. It was also found that the Al composition dependence of exciton localization energy of AlGaN alloys is inconsistent with that of the excitonic linewidth. We contribute the inconsistency to the strong zero-dimensional exciton localization.
RESUMO
A sample of the ß-Ga2O3/wurtzite GaN heterostructure has been grown by dry thermal oxidation of GaN on a sapphire substrate. X-ray diffraction measurements show that the ß-Ga2O3 layer was formed epitaxially on GaN. The valence band offset of the ß-Ga2O3/wurtzite GaN heterostructure is measured by X-ray photoelectron spectroscopy. It is demonstrated that the valence band of the ß-Ga2O3/GaN structure is 1.40 ± 0.08 eV.
