InGaN-based green light-emitting diodes （LEDs） with different growth temperatures of superlattice grown on Si （111） substrates are investigated by temperature-dependent electroluminescence between 100 K and 350K. ...InGaN-based green light-emitting diodes （LEDs） with different growth temperatures of superlattice grown on Si （111） substrates are investigated by temperature-dependent electroluminescence between 100 K and 350K. It is observed that with the decrease of the growth temperature of the superlattice from 895℃ to 855℃, the forward voltage decreases, especially at low temperature. We presume that this is due to the existence of the larger average size of V-shaped pits, which is determined by secondary ion mass spectrometer measurements. Meanwhile, the sample with higher growth temperature of superlattice shows a severer efficiency droop at cryogenic temperatures （about 100 K-150 K）. Electron overflow into p-GaN is considered to be the cause of such phenomena, which is relevant to the poorer hole injection into multiple quantum wells and the more reduced effective active volume in the active region.展开更多
The transparent and thermal developments of high-purity Al_2O_3 doped with different levels of Nd_2O_3 were investigated. Dopant levels ranged from 500–1500 ppm（Nd/Al atomic ratio）. The samples were characterized w...The transparent and thermal developments of high-purity Al_2O_3 doped with different levels of Nd_2O_3 were investigated. Dopant levels ranged from 500–1500 ppm（Nd/Al atomic ratio）. The samples were characterized with X-ray diffraction（XRD）, scanning electron microscopy（SEM）, Raman spectroscopy, transmittance spectroscopy and specific heat measurement. Results revealed that with proper Nd doped, Nd^（3＋） ions solid dissolved in Al_2O_3 lattice, resulting in small and uniform grain and high bonding vibration, which was beneficial to transparent and thermal properties. With 1000 ppm Nd doped, Al_2O_3 translucent ceramics showed a total transmittance of 89% and thermal conductivity of 41.7 W/m/K, indicating a potential application as substrate for effective heat dissipation and multi emitting surface in LEDs module.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 61334001the National Key Research and Development Program of China under Grant Nos 2016YFB0400600,2016YFB0400601 and 2016YFB0400100+1 种基金the National Science Foundation for Young Scientists of China under Grant No 21405076the Fund for Less Developed Regions of the National Natural Science Foundation of China under Grant No 11364034
文摘InGaN-based green light-emitting diodes （LEDs） with different growth temperatures of superlattice grown on Si （111） substrates are investigated by temperature-dependent electroluminescence between 100 K and 350K. It is observed that with the decrease of the growth temperature of the superlattice from 895℃ to 855℃, the forward voltage decreases, especially at low temperature. We presume that this is due to the existence of the larger average size of V-shaped pits, which is determined by secondary ion mass spectrometer measurements. Meanwhile, the sample with higher growth temperature of superlattice shows a severer efficiency droop at cryogenic temperatures （about 100 K-150 K）. Electron overflow into p-GaN is considered to be the cause of such phenomena, which is relevant to the poorer hole injection into multiple quantum wells and the more reduced effective active volume in the active region.
基金supported by the project of Natural Science Foundation of Zhejiang Province(LY15F050005 and LZ14B010001)
文摘The transparent and thermal developments of high-purity Al_2O_3 doped with different levels of Nd_2O_3 were investigated. Dopant levels ranged from 500–1500 ppm（Nd/Al atomic ratio）. The samples were characterized with X-ray diffraction（XRD）, scanning electron microscopy（SEM）, Raman spectroscopy, transmittance spectroscopy and specific heat measurement. Results revealed that with proper Nd doped, Nd^（3＋） ions solid dissolved in Al_2O_3 lattice, resulting in small and uniform grain and high bonding vibration, which was beneficial to transparent and thermal properties. With 1000 ppm Nd doped, Al_2O_3 translucent ceramics showed a total transmittance of 89% and thermal conductivity of 41.7 W/m/K, indicating a potential application as substrate for effective heat dissipation and multi emitting surface in LEDs module.
