In Ga N light-emitting diodes(LEDs) with Ga N/In Ga N/Al Ga N/In Ga N/Ga N composition-graded barriers are proposed to replace the sixth and the middle five Ga N barriers under the condition of removing the electron...In Ga N light-emitting diodes(LEDs) with Ga N/In Ga N/Al Ga N/In Ga N/Ga N composition-graded barriers are proposed to replace the sixth and the middle five Ga N barriers under the condition of removing the electron blocking layer(EBL)and studied numerically in this paper. Simulation results show that the specially designed barrier in the sixth barrier is able to modulate the distributions of the holes and electrons in quantum well which is adjacent to the specially designed barrier. Concretely speaking, the new barrier could enhance both the electron and hole concentration remarkably in the previous well and reduce the hole concentration for the latter one to some extent along the growth direction. What is more,a phenomenon, i.e., a better carrier distribution in all the wells, just appears with the adoption of the new barriers in the middle five barriers, resulting in a much higher light output power and a lower efficiency droop than those in a conventional LED structure.展开更多
The physical effects of the carrier distribution in the channel on the dynamical performance of a static induction thyristor (SITH) have been studied numerically and experimentally. The analytical expressions of the...The physical effects of the carrier distribution in the channel on the dynamical performance of a static induction thyristor (SITH) have been studied numerically and experimentally. The analytical expressions of the minority carrier distribution in the channel of the SITH were also derived and the space charge distribution control- ling mechanism on the current of the SITH under high level injection have been analyzed deeply. The relationships among the minority carrier distribution, potential distribution, I-V characteristics and transient performances of the SITH are revealed.展开更多
The effect of different barriers between green and blue light regions in dual wavelength light emitting diodes was studied. Compared with a traditional sample, electroluminescence and photoluminescence spectra of the ...The effect of different barriers between green and blue light regions in dual wavelength light emitting diodes was studied. Compared with a traditional sample, electroluminescence and photoluminescence spectra of the newly designed samples showed peak intensity improvements and smaller blue-shifts with increasing injection current level, and the bottom quantum-wells light emitting is enhanced. All these phenomena can be ascribed to reduced barrier thickness and indium doping in the quantum-barrier influencing electric fields and more holes injecting into the bottom QWs.展开更多
Narrowband photodetectors conventionally rely on optical structure design orbandpass filters to achieve the narrowband regime. Recently, a strategy forfilterless narrowband photoresponse based on the charge collection...Narrowband photodetectors conventionally rely on optical structure design orbandpass filters to achieve the narrowband regime. Recently, a strategy forfilterless narrowband photoresponse based on the charge collection narrowing(CCN) mechanism was reported. However, the CCN strategy requires an electrically and optically “thick” photoactive layer, which poses challenges in controlling the narrowband photoresponse. Here we propose a novel strategy forconstructing narrowband photodetectors by leveraging the inherent ion migration in perovskites, which we term “band modulation narrowing” (BMN). Bymanipulating the ion migration with external stimuli such as illumination,temperature, and bias voltage, we can regulate in situ the energy-band structure of perovskite photodetectors (PPDs) and hence their spectral response.Combining the Fermi energy levels obtained by the Kelvin probe force microscopy, the internal potential profiles from solar cell capacitance simulator simulation, and the anion accumulation revealed by the transient ion-drifttechnique, we discover two critical mechanisms behind our BMN strategy: theextension of an optically active but electronically dead region proximal to the top electrode and the down-bending energy bands near the electron transportlayer. Our findings offer a case for harnessing the often-annoying ionmigration for developing advanced narrowband PPDs.展开更多
The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights(BH) of as-deposited and 200 ℃ annealed SBDs are 0.80 eV(I-V)/0....The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights(BH) of as-deposited and 200 ℃ annealed SBDs are 0.80 eV(I-V)/0.93 eV(C-V) and 0.87 eV(I-V)/1.03 eV(C-V). However, the BH rises to 0.99 eV(I-V)/1.18 eV(C-V)and then slightly deceases to 0.92 eV(I-V)/1.03 eV(C-V) after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung's functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung's and ΨS-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.展开更多
基金Project supported by the Science and Technology Program Project for the Innovation of Forefront and Key Technology of Guangdong Province,China(Grant No.2014B010121001)the Special Funds for Strategic Emerging Industries of Guangdong Province,China(Grant No.2012A080304006)+3 种基金the Special Funds for the Innovation of Forefront and Key Technology of Guangdong Province,China(Grant No.2014B010119004)the Science and Technology Program Project for High Conversion Efficiency and Application of Direct Driver High-end LED Chip of Guangdong Province,China(Grant No.2013B010204065)the Special Project for Key Science and Technology of Zhongshan City,Guangdong Province,China(Grant No.2014A2FC204)the Science and Technology Program Project in Huadu District of Guangzhou City,China(Grant No.HD15PT003)
文摘In Ga N light-emitting diodes(LEDs) with Ga N/In Ga N/Al Ga N/In Ga N/Ga N composition-graded barriers are proposed to replace the sixth and the middle five Ga N barriers under the condition of removing the electron blocking layer(EBL)and studied numerically in this paper. Simulation results show that the specially designed barrier in the sixth barrier is able to modulate the distributions of the holes and electrons in quantum well which is adjacent to the specially designed barrier. Concretely speaking, the new barrier could enhance both the electron and hole concentration remarkably in the previous well and reduce the hole concentration for the latter one to some extent along the growth direction. What is more,a phenomenon, i.e., a better carrier distribution in all the wells, just appears with the adoption of the new barriers in the middle five barriers, resulting in a much higher light output power and a lower efficiency droop than those in a conventional LED structure.
基金Project supported by the National Natural Science Foundation of China(No.61366006)the Scientific and Technological Supporting Programme of Gansu Province,China(No.1304GKCA012)
文摘The physical effects of the carrier distribution in the channel on the dynamical performance of a static induction thyristor (SITH) have been studied numerically and experimentally. The analytical expressions of the minority carrier distribution in the channel of the SITH were also derived and the space charge distribution control- ling mechanism on the current of the SITH under high level injection have been analyzed deeply. The relationships among the minority carrier distribution, potential distribution, I-V characteristics and transient performances of the SITH are revealed.
基金supported by the National Natural Science Foundation of China(No.61274040)
文摘The effect of different barriers between green and blue light regions in dual wavelength light emitting diodes was studied. Compared with a traditional sample, electroluminescence and photoluminescence spectra of the newly designed samples showed peak intensity improvements and smaller blue-shifts with increasing injection current level, and the bottom quantum-wells light emitting is enhanced. All these phenomena can be ascribed to reduced barrier thickness and indium doping in the quantum-barrier influencing electric fields and more holes injecting into the bottom QWs.
基金National Natural Science Foundation of China,Grant/Award Numbers:21972006,22275180,U2001217,22261160370,52202182Shenzhen Peacock plan,Grant/Award Number:KQTD2016053015544057+1 种基金Shenzhen Innovation Fund,Grant/Award Number:JCYJ20220818101018038Natural Sciences and Engineering Research Council of Canada,Grant/Award Number:RGPIN-2020-04239。
文摘Narrowband photodetectors conventionally rely on optical structure design orbandpass filters to achieve the narrowband regime. Recently, a strategy forfilterless narrowband photoresponse based on the charge collection narrowing(CCN) mechanism was reported. However, the CCN strategy requires an electrically and optically “thick” photoactive layer, which poses challenges in controlling the narrowband photoresponse. Here we propose a novel strategy forconstructing narrowband photodetectors by leveraging the inherent ion migration in perovskites, which we term “band modulation narrowing” (BMN). Bymanipulating the ion migration with external stimuli such as illumination,temperature, and bias voltage, we can regulate in situ the energy-band structure of perovskite photodetectors (PPDs) and hence their spectral response.Combining the Fermi energy levels obtained by the Kelvin probe force microscopy, the internal potential profiles from solar cell capacitance simulator simulation, and the anion accumulation revealed by the transient ion-drifttechnique, we discover two critical mechanisms behind our BMN strategy: theextension of an optically active but electronically dead region proximal to the top electrode and the down-bending energy bands near the electron transportlayer. Our findings offer a case for harnessing the often-annoying ionmigration for developing advanced narrowband PPDs.
文摘The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights(BH) of as-deposited and 200 ℃ annealed SBDs are 0.80 eV(I-V)/0.93 eV(C-V) and 0.87 eV(I-V)/1.03 eV(C-V). However, the BH rises to 0.99 eV(I-V)/1.18 eV(C-V)and then slightly deceases to 0.92 eV(I-V)/1.03 eV(C-V) after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung's functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung's and ΨS-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.