Thermal stability of ZnMgSSe/ZnSe laser heterostructures

Optically pumped lasing and photoluminescence of ZnMgSSe/ZnSe quantum wells grown by MOVPE were studied in a temperature interval of 78-650 K. The technique of spectrum imaging in a transmission electron microscope with energy filter and two-dimensional detector was applied to ZnMgSSe/ZnSe multiple quantum well laser structures. It was found that the main degradation mechanism of the ZnMgSSe/ZnSe heterostructures at temperatures higher than 450 K is the diffusion of S atoms from the barriers into the quantum wells which leads to increasing point defect concentrations in the active layers of the lasers. It was established that the inherent laser radiation decreases the defect concentration and reduces the laser threshold in the optically pumped ZnMgSSe/ZnSe quantum well lasers after their thermal degradation at T=450-650 K. Quantitative S profiles are extracted from this quaternary system. From a comparison of as-grown and annealed structures, the diffusivity of S has been calculated to 6·10^-22 m² s^-1 at T=550 K