Organics-capped ZnSe quantum dots were synthesized by a colloidal chemical approach using ZnO and Se powder as precursors. The photoluminescence of the specimens showed strong white emission ͑ϳ200 nm full width at half maximum͒ in the visible range under ambient conditions. The white emission was attributed to the mixing of blue emission of ZnSe nanocrystals exhibiting quantum confinement effect with green-red emission of radiative deep levels from ZnSe surface strained lattice. Based on organic-capped ZnSe quantum dots, the white-light-emitting diodes were fabricated using a near-UV InGaN chip as the excitation source. The diodes emitted white light with CIE chromaticity coordinates of ͑0.38 and 0.41͒ and show great potential for use in lighting applications.

No abstract

Far-field distributions of GaN-based photonic crystal (PhC) film-transferred light-emitting diodes (FT-LEDs) were investigated. The thickness of the device is about 840 nm. The emission wavelength is around 520 nm. The PhC region is a square lattice with a/lambda around 0.5. Angular-resolved measurements in the Gamma-X and Gamma-M directions were made in the polarized-resolved manner. Guided mode extraction behavior in agreement with the two-dimensional free-photon band calculation was observed. In addition, the pseudo-TM behavior for the non-collinearly coupled modes was observed. The azimuthal-mapping of the angular-resolved spectra revealed the evolution of the collinearly and the non-collinearly coupled modes. Furthermore, the light enhancement of approximately 2.7x and the collimation angle about 102.3 degrees were achieved.

Articles you may be interested inEnhancement of operation temperature of In As ∕ Ga As quantum-dot infrared photodetectors with hydrogenplasma treatment Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector In this article, quantum-dot infrared photodetectors ͑QDIPs͒ with 10-and 30-period InAs/ GaAs quantum-dot structures are investigated. High responsivity of 2.37 A / W and detectivity of 2.48 ϫ 10 10 cm Hz 1/2 / W for 30-period QDIPs under 10 K are observed at −2.7 and 1.2 V, respectively. Almost symmetric photocurrents and dark currents under positive and negative biases are observed for both devices, which indicate a minor influence of the wetting layer on the performance of QDIPs. Lower dark current and increased photocurrent for the 30-period QDIPs would predict a better performance for devices with over a 30-period QD structure.