In GaN-based green light-emitting diodes（LEDs） with and without Mg-preflow before the growth of p-Al GaN electron blocking layer（EBL） are investigated experimentally.A higher Mg doping concentration is achieved in...In GaN-based green light-emitting diodes（LEDs） with and without Mg-preflow before the growth of p-Al GaN electron blocking layer（EBL） are investigated experimentally.A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment,effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures.However,unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature.Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions.Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to pGaN side through the（8-plane rather than the V-shape pits,which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN.Within this framework,apparently disparate experimental observations regarding electroluminescence properties,in this work,are well reconciled.展开更多
We have performed a full numerical calculation of the Franz-Keldysh （FK） effect on magnetoexcitons in a bulk GaAs semiconductor. By employing an initial wlue method in combination with the application of a perfect m...We have performed a full numerical calculation of the Franz-Keldysh （FK） effect on magnetoexcitons in a bulk GaAs semiconductor. By employing an initial wlue method in combination with the application of a perfect matched layer, the numerical effort and storage size are dramatically reduced due to a significant reduction in both computed domain and number of base functions. In the absence of an electric field, the higher magnetoexcitonic peaks show distinct Fano lineshape due to the degeneracy with continuum states of the lower Landau levels. The magnetoexcitons that belong to the zeroth Landau level remain in bound states and lead to Lorentzian lineshape, because they are not degenerated with continuum states. In the presence of an electric field, the FK effect on each magnetoexcitonic resonance can be identified for high magnetic fields. However, for low magnetic fields, the FK oscillations dominate the spectrum structure in the vicinity of the bandgap edge and the magnetoexcitonic resonances dominate the spectrum structure of higher energies. In the moderate electric fields, the interplay of FK effect and magnetoexcitonic resonance leads to a complex and rich structure in the absorption spectrum.展开更多
ALTHOUGH electroluminescence(EL)from silicon anodes in contact with various electrolyteswas first reported by Gee in 1960,it did not attract much attention until Canham in 1990obtained highly efficient visible photolu...ALTHOUGH electroluminescence(EL)from silicon anodes in contact with various electrolyteswas first reported by Gee in 1960,it did not attract much attention until Canham in 1990obtained highly efficient visible photoluminescence(PL)on porous silicon(PS)at room tem-perature.This is important for both fundamental interest in nanocrystalline展开更多
The electroluminescence （EL） and photoluminescence （PL） spectra of InGaN/GaN multiple quantum wells （MQWs） with a prestrained InGaN interlayer in a laser diode structure are investigated. When the injection curr...The electroluminescence （EL） and photoluminescence （PL） spectra of InGaN/GaN multiple quantum wells （MQWs） with a prestrained InGaN interlayer in a laser diode structure are investigated. When the injection current increases from 5 mA to 50 mA, the blueshift of the EL emission peak is 1 meV for the prestrained sample and 23 meV for a control sample with the conventional structure. Also, the internal quantum efficiency and the EL intensity at the injection current of 20 mA are increased by 71% and 65% respectively by inserting the prestrained InGaN interlayer. The reduced blueshift and the enhanced emission are attributed mainly to the reduced quantum-confined Stark effect （QCSE） in the prestrained sample. Such attributions are supported by the theoretical simulation results, which reveal the smaller piezoelectric field and the enhanced overlap of electron and hole wave functions in the prestrained sample. Therefore, the prestrained InGaN interlayer contributes to strain relaxation in the MQW layer and enhancement of light emission due to the reduction of QCSE.展开更多
利用ZnS…Cu电致发光粉末与环氧树脂胶混合,设计制作了一种梯形电极结构的电压传感单元,实现了电致发光电压传感器输出信号的温度漂移补偿。电致发光电压传感信号通过2根塑料光纤传输到2个硅光电探测器,并选择其开路电压作为传感器的输...利用ZnS…Cu电致发光粉末与环氧树脂胶混合,设计制作了一种梯形电极结构的电压传感单元,实现了电致发光电压传感器输出信号的温度漂移补偿。电致发光电压传感信号通过2根塑料光纤传输到2个硅光电探测器,并选择其开路电压作为传感器的输出信号。在同一外加电压条件下,梯形电极区域内的电场分布是不均匀的,因而不同场点的发光亮度不同。通过测量梯形电极区域内2个不同发光点的发光强度随外加电压的变化,并对两路输出电压传感信号进行数据拟合与计算,可获知被测电压的有效值,并可实现对输出信号温度漂移的补偿。在-40~60℃范围内,采用上述温度漂移补偿方法测量了有效值在0.7~1.5 k V范围内的工频电压,传感器输出信号的非线性误差低于1.6%,验证了该温度漂移补偿方法的有效性。展开更多
The voltage\|tuned electroluminescence (EL) of n\|type porous silicon (PS) in a persulphate solution under cathodic polarization was studied. A blue shift with the increase of cathodic polarization and a time\|depende...The voltage\|tuned electroluminescence (EL) of n\|type porous silicon (PS) in a persulphate solution under cathodic polarization was studied. A blue shift with the increase of cathodic polarization and a time\|dependent red shift at constant potential of EL spectra have been observed. To investigate the voltage tuning mechanism and luminescence quenching mechanism for the electroluminescence of PS, FT\|IR, AFM and electrochemical methods were used. The results show that the voltage\|tuned electroluminescence can be attributed to the selective excitation of different sizes of PS crystallites, which agrees with the "quantum confinement model" in PS luminescence.展开更多
基金Supported by the National Key R&D Program of China under Grant Nos 2016YFB0400600 and 2016YFB0400601the State Key Program of the National Natural Science of China under Grant No 61334001+2 种基金the Key R&D Program of Jiangxi Province under Grant No 20165ABC28007the Natural Science Foundation of Jiangxi Province under Grant No 20151BAB207053the National Natural Science Foundation of China under Grant No 21405076
文摘In GaN-based green light-emitting diodes（LEDs） with and without Mg-preflow before the growth of p-Al GaN electron blocking layer（EBL） are investigated experimentally.A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment,effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures.However,unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature.Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions.Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to pGaN side through the（8-plane rather than the V-shape pits,which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN.Within this framework,apparently disparate experimental observations regarding electroluminescence properties,in this work,are well reconciled.
基金Project supported by the Major Program of the National Natural Science Foundation of China （Grant No 10390160）, and the National Natural Science Foundation of China （Grant No 30370420）.
文摘We have performed a full numerical calculation of the Franz-Keldysh （FK） effect on magnetoexcitons in a bulk GaAs semiconductor. By employing an initial wlue method in combination with the application of a perfect matched layer, the numerical effort and storage size are dramatically reduced due to a significant reduction in both computed domain and number of base functions. In the absence of an electric field, the higher magnetoexcitonic peaks show distinct Fano lineshape due to the degeneracy with continuum states of the lower Landau levels. The magnetoexcitons that belong to the zeroth Landau level remain in bound states and lead to Lorentzian lineshape, because they are not degenerated with continuum states. In the presence of an electric field, the FK effect on each magnetoexcitonic resonance can be identified for high magnetic fields. However, for low magnetic fields, the FK oscillations dominate the spectrum structure in the vicinity of the bandgap edge and the magnetoexcitonic resonances dominate the spectrum structure of higher energies. In the moderate electric fields, the interplay of FK effect and magnetoexcitonic resonance leads to a complex and rich structure in the absorption spectrum.
文摘ALTHOUGH electroluminescence(EL)from silicon anodes in contact with various electrolyteswas first reported by Gee in 1960,it did not attract much attention until Canham in 1990obtained highly efficient visible photoluminescence(PL)on porous silicon(PS)at room tem-perature.This is important for both fundamental interest in nanocrystalline
基金Project supported by the National Basic Research Program of China(Grant No.2012CB619304)the National Natural Science Foundation of China(Grant Nos.61076013 and 51272008)the Beijing Municipal Science and Technology Project,China(Grant No.H030430020000)
文摘The electroluminescence （EL） and photoluminescence （PL） spectra of InGaN/GaN multiple quantum wells （MQWs） with a prestrained InGaN interlayer in a laser diode structure are investigated. When the injection current increases from 5 mA to 50 mA, the blueshift of the EL emission peak is 1 meV for the prestrained sample and 23 meV for a control sample with the conventional structure. Also, the internal quantum efficiency and the EL intensity at the injection current of 20 mA are increased by 71% and 65% respectively by inserting the prestrained InGaN interlayer. The reduced blueshift and the enhanced emission are attributed mainly to the reduced quantum-confined Stark effect （QCSE） in the prestrained sample. Such attributions are supported by the theoretical simulation results, which reveal the smaller piezoelectric field and the enhanced overlap of electron and hole wave functions in the prestrained sample. Therefore, the prestrained InGaN interlayer contributes to strain relaxation in the MQW layer and enhancement of light emission due to the reduction of QCSE.
文摘利用ZnS…Cu电致发光粉末与环氧树脂胶混合,设计制作了一种梯形电极结构的电压传感单元,实现了电致发光电压传感器输出信号的温度漂移补偿。电致发光电压传感信号通过2根塑料光纤传输到2个硅光电探测器,并选择其开路电压作为传感器的输出信号。在同一外加电压条件下,梯形电极区域内的电场分布是不均匀的,因而不同场点的发光亮度不同。通过测量梯形电极区域内2个不同发光点的发光强度随外加电压的变化,并对两路输出电压传感信号进行数据拟合与计算,可获知被测电压的有效值,并可实现对输出信号温度漂移的补偿。在-40~60℃范围内,采用上述温度漂移补偿方法测量了有效值在0.7~1.5 k V范围内的工频电压,传感器输出信号的非线性误差低于1.6%,验证了该温度漂移补偿方法的有效性。
文摘The voltage\|tuned electroluminescence (EL) of n\|type porous silicon (PS) in a persulphate solution under cathodic polarization was studied. A blue shift with the increase of cathodic polarization and a time\|dependent red shift at constant potential of EL spectra have been observed. To investigate the voltage tuning mechanism and luminescence quenching mechanism for the electroluminescence of PS, FT\|IR, AFM and electrochemical methods were used. The results show that the voltage\|tuned electroluminescence can be attributed to the selective excitation of different sizes of PS crystallites, which agrees with the "quantum confinement model" in PS luminescence.
