Optical Investigation On InGaN/GaN Multiple Quantum Wells

Due to excellent electrochemical properties, GaN-based materials have been widely used in microelectronics and optoelectronics fields. GaN-based materials is a direct band gap semiconductor material, adjusting alloy composition, the band gap can be ranging from InN (0.7eV) to AlN (6.28eV),covering the entire visible light district. With the development of semiconductor technology, blue, green、UV LED devices have been successfully prepared, and blue LED has become the world’s major research focus. However, because of large lattice mismatch and thermal mismatch between the sapphire substrate and the GaN, when growing crystal there will be a high dislocation density resulting In lower luminous efficiency. InN and GaN mutual solubility is very low, and the saturation vapor pressure is different. When growing InGaN/GaN multiple quantum wells, the Inhomogeneous distribution of In component forms localized states. The current view is that it is precisely because of these localized states improves the LED luminous efficiency, but contained within the InGaN/GaN multiple quantum wells carriers kinetic mechanism is not yet fully clear understanding. This paper studies the InGaN/GaN multiple quantum well light-emitting properties by photoluminescence and electro-luminescence experimental methods, the main contents are as follows:1.Temperature dependence of photoluminescence. In the low excitation power, with temperature Increased the peak showed red shift-blue shift-red shift,"S-shape", which could be attributed to the effect of rich-In localized states. In large excitation power, the peak energy and FWHM were different, resulting from the saturated localized states filling high energy level of localized states played a leading role.2.Power dependence of photoluminescence. At low temperature, In the low power range with the excitation power Increases the peak energy had been blue-shifted and FWHM decreased, resulting from the Influence of Stark effect. With the excitation power further Increased, band-filling played a leading role resulted peak energy blue-shift and FWHM Increased. At room temperature, nonradiative recombination centers were activated, so In low power nonradiative recombination played a dominant role leading to the peak position red-shift, FWHM Increased.3.ElectrolμmInescent characteristics. At low temperature and room temperature under a large current, the applied electric field produced a great Influence on the quantum well, resulting In a reduced efficiency of the phenomenon. Through the study of variable thickness of the EBL, we found that with the Increase of the EBL the light-emitting peak red shifted, This was because the Increase of the quantum well polarization field.