Wavelength-Shifted Yellow Electroluminescence of Si Quantum-Dot Embedded 20-Pair SiNx/SiOx Superlattice by Ostwald Ripening Effect

Yellow electroluminescence (EL) of a 20-pair Si-rich SiN_x /SiO_x superlattice is demonstrated by plasma-enhanced chemical vapor deposition (PECVD) and annealing process. After annealing at 900^°C for 30 min, two photoluminescence (PL) peaks at 480 and 570 nm are observed to blue-shift the PL wavelength, and the corresponding peak intensity is enhanced due to the self-aggregation of Si quantum dots (QDs). When increasing the annealing temperature to 1050^°C , the PL peaks caused by the aggregated Si-QDs in SiN_x and SiO_x layers red-shift to 500 and 600 nm, thereby shifting the PL peak wavelength to 520 nm. Such a wavelength red-shifting phenomenon is mainly attributed to the formation of large Si-QDs due to the Ostwald ripening effect. The turn-on voltage and the V-I slope of the ITO/SiN_x/SiO_x/p-Si/Al LED device are 200 V and 15.5 kV/mA with Fowler-Nordheim (FN) tunneling assistant carrier transport under an effective barrier height of 1.3 eV. Maximum output-power-current slope of 0.2 μW/A at power conversion efficiency of 10^-6 is detected.