In GaN-based green light-emitting diodes（LEDs） with different green quantum well numbers grown on Si（111）substrates by metal organic chemical vapor deposition are investigated. It is observed that V-shaped pits ap...In GaN-based green light-emitting diodes（LEDs） with different green quantum well numbers grown on Si（111）substrates by metal organic chemical vapor deposition are investigated. It is observed that V-shaped pits appear in the AFM images with the green quantum well number increasing from 5 to 9, and results in larger reverse-bias leakage current. Meanwhile, in the case of the sample with the number from 5 to 7 then to 9, the external quantum efficiency increases firstly, and then decreases. These phenomena may be related to the size of V-shaped pits in the active area and the distribution of electrons and holes in the active area caused by V-shaped pits. The optimal number of green quantum wells is determined to be 7.展开更多
The effect of back-diffusion of Mg dopants on optoelectronic characteristics of InGaN-based green light-emitting diodes （LEDs） is investigated. The LEDs with less Mg back-diffusion show blue shifts of longer wavelen...The effect of back-diffusion of Mg dopants on optoelectronic characteristics of InGaN-based green light-emitting diodes （LEDs） is investigated. The LEDs with less Mg back-diffusion show blue shifts of longer wavelengths and larger wavelengths with the increasing current, which results from the Mg-dopant-related polarization screening. The LEDs show enhanced efficiency with the decreasing Mg back-diffusion in the lower current region. Light outputs follow the power law L α I^m, with smaller parameter m in the LEDs with less Mg back-diffusion, indicating a lower density of trap states. The trap-assisted tunneling current is also suppressed by reducing Mg- defect-related nonradiative centers in the active region. Furthermore, the forward current-voltage characteristics are improved.展开更多
Wild rice is an important resource of usefulgenes to rice breeders. However, low regener-ation frequency is an obstacle to use the valu-able genes. We used desiccation to improve theregeneration frequency and studied ...Wild rice is an important resource of usefulgenes to rice breeders. However, low regener-ation frequency is an obstacle to use the valu-able genes. We used desiccation to improve theregeneration frequency and studied the bio-chemical changes of calli of wild rice after des-iccation.Materials used in this experiment werewild species O. rufipogon, O. meyeriana, O.alta, and O. brachyantha. Young panicles(0.1-0. 5 cm in length of the inflorescence)展开更多
In present paper, the non-equilibrium Green function(NEGF) method along with the density functional theory(DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne(...In present paper, the non-equilibrium Green function(NEGF) method along with the density functional theory(DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne(γ-graphyne) nanoribbons. The results show that all the studied nanoribbons are semiconductor and their band gaps decrease as the widths of nanoribbons increase, which will result in increasing current at a certain voltage. Also our results show the promising application of armchair graphyne nanoribbons in nano-electrical devices.展开更多
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFB0400601the National Natural Science Foundation of China under Grant Nos 61704069,11674147,61604066,51602141 and 11604137
文摘In GaN-based green light-emitting diodes（LEDs） with different green quantum well numbers grown on Si（111）substrates by metal organic chemical vapor deposition are investigated. It is observed that V-shaped pits appear in the AFM images with the green quantum well number increasing from 5 to 9, and results in larger reverse-bias leakage current. Meanwhile, in the case of the sample with the number from 5 to 7 then to 9, the external quantum efficiency increases firstly, and then decreases. These phenomena may be related to the size of V-shaped pits in the active area and the distribution of electrons and holes in the active area caused by V-shaped pits. The optimal number of green quantum wells is determined to be 7.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61505197 and 61334009the National High-Technology Research and Development Program of China under Grant No 2014AA032604
文摘The effect of back-diffusion of Mg dopants on optoelectronic characteristics of InGaN-based green light-emitting diodes （LEDs） is investigated. The LEDs with less Mg back-diffusion show blue shifts of longer wavelengths and larger wavelengths with the increasing current, which results from the Mg-dopant-related polarization screening. The LEDs show enhanced efficiency with the decreasing Mg back-diffusion in the lower current region. Light outputs follow the power law L α I^m, with smaller parameter m in the LEDs with less Mg back-diffusion, indicating a lower density of trap states. The trap-assisted tunneling current is also suppressed by reducing Mg- defect-related nonradiative centers in the active region. Furthermore, the forward current-voltage characteristics are improved.
文摘Wild rice is an important resource of usefulgenes to rice breeders. However, low regener-ation frequency is an obstacle to use the valu-able genes. We used desiccation to improve theregeneration frequency and studied the bio-chemical changes of calli of wild rice after des-iccation.Materials used in this experiment werewild species O. rufipogon, O. meyeriana, O.alta, and O. brachyantha. Young panicles(0.1-0. 5 cm in length of the inflorescence)
文摘In present paper, the non-equilibrium Green function(NEGF) method along with the density functional theory(DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne(γ-graphyne) nanoribbons. The results show that all the studied nanoribbons are semiconductor and their band gaps decrease as the widths of nanoribbons increase, which will result in increasing current at a certain voltage. Also our results show the promising application of armchair graphyne nanoribbons in nano-electrical devices.
