It is well known that -nitride semiconductors can generate the magnitude of MV/cm polarization electric field which is comparable with their ionization electric fields. To take full advantage of the polarization elect...It is well known that -nitride semiconductors can generate the magnitude of MV/cm polarization electric field which is comparable with their ionization electric fields. To take full advantage of the polarization electric field, we design an N-face AlGaN solar-blind avalanche photodiode (APD) with an Al<sub>0.45</sub>Ga<sub>0.55</sub>N/Al<sub>0.3</sub>Ga<sub>0.7</sub>N heterostructure as separate absorption and multiplication (SAM) regions. The simulation results show that the N-face APDs are more beneficial to improving the avalanche gain and reducing the avalanche breakdown voltage compared with the Ga-face APDs due to the effect of the polarization electric field. Furthermore, the Al<sub>0.45</sub>Ga<sub>0.55</sub>N/Al<sub>0.3</sub>Ga<sub>0.7</sub>N heterostructure SAM regions used in APDs instead of homogeneous Al<sub>0.45</sub>Ga<sub>0.55</sub>N SAM structure can increase significantly avalanche gain because of the increased hole ionization coefficient by using the relatively low Al-content AlGaN in the multiplication region. Meanwhile, a quarter-wave AlGaN/AlN distributed Bragg reflector structure at the bottom of the device is designed to remain a solar-blind characteristic of the heterostructure SAM-APDs.展开更多
For absorption linewidth inversion with wavelength modulation spectroscopy（WMS）, an optimized WMS spectral line fitting method was demonstrated to infer absorption linewidth effectively, and the analytical expressio...For absorption linewidth inversion with wavelength modulation spectroscopy（WMS）, an optimized WMS spectral line fitting method was demonstrated to infer absorption linewidth effectively, and the analytical expressions for relationships between Lorentzian linewidth and the separations of first harmonic peak-to-valley and second harmonic zero-crossing were deduced. The transition of CO_2 centered at 4991.25 cm^（-1） was used to verify the optimized spectral fitting method and the analytical expressions. Results showed that the optimized spectra fitting method was able to infer absorption accurately and compute more than 10 times faster than the commonly used numerical fitting procedure. The second harmonic zero-crossing separation method calculated an even 6 orders faster than the spectra fitting without losing any accuracy for Lorentzian dominated cases. Additionally, linewidth calculated through second harmonic zero-crossing was preferred for much smaller error than the first harmonic peak-to-valley separation method. The presented analytical expressions can also be used in on-line optical sensing applications, electron paramagnetic resonance, and further theoretical characterization of absorption lineshape.展开更多
A Ga_(2)O_(3)/diamond separate absorption and multiplication avalanche photodiode(SAM-APD)with mesa structure has been proposed and simulated.The simulation is based on an optimized Ga_(2)O_(3)/diamond heterostructure...A Ga_(2)O_(3)/diamond separate absorption and multiplication avalanche photodiode(SAM-APD)with mesa structure has been proposed and simulated.The simulation is based on an optimized Ga_(2)O_(3)/diamond heterostructure TCAD physical model,which is revised by repeated comparison with the experimental data from the literature.Since both Ga_(2)O_(3)and diamond are ultra-wide bandgap semiconductor materials,the Ga_(2)O_(3)/diamond SAM-APD shows good solar-blind detection ability,and the corresponding cutoff wavelength is about 263 nm.The doping distribution and the electric field distribution of the SAM-APD are discussed,and the simulation results show that the gain of the designed device can reach 5×10^(4)and the peak responsivity can reach a value as high as 78 A/W.展开更多
Magnesium(Mg)is globally abundant in resources,and Mg‐based compounds—such as magnesium based hydrides,hydroxides,oxides,and magnesium metal‐organic frameworks(Mg MOFs)—have shown significant application prospects...Magnesium(Mg)is globally abundant in resources,and Mg‐based compounds—such as magnesium based hydrides,hydroxides,oxides,and magnesium metal‐organic frameworks(Mg MOFs)—have shown significant application prospects in gas separation.This is largely due to the electronic characteristics of Mg or Mg^(2+)ions,which facilitate the capture of hydrogen(H_(2))and acidic gases such as carbon dioxide(CO_(2))and sulfur dioxide(SO_(2))from other gases.Consequently,exploring the use of Mgbased materials in gas separation and purification applications could not only advance the scientific understanding of solid‐gas interaction mechanisms but also provide cost‐effective solutions for gas separation technology at an industrial level.This review summarizes the recent practices and explorations of Mg‐based solid‐state materials in various gas separation and purification methods,including physical adsorption‐based separation,chemical absorption‐based separation,and membrane‐based separation.For each separation method,the relevant Mg‐based materials are discussed in detail,and key findings from existing research are presented and analyzed.Additionally,inspired by the straightforward design of air‐stable hydrogen storage materials,this review specifically addresses anti‐passivation strategies for Mg‐based hydrides,which are crucial for their applications in hydrogen gas separation and purification.Finally,this review highlights key issues and fields for future research and development in Mg‐based gas separation materials.展开更多
This paper presents a new method to increase the speed of the separated absorption, grading, charge, and multiplication avalanche photodiode （SAGCM-APD）. This improvement is obtained by adding a new thin charge laye...This paper presents a new method to increase the speed of the separated absorption, grading, charge, and multiplication avalanche photodiode （SAGCM-APD）. This improvement is obtained by adding a new thin charge layer between absorption and grading layers, with assuming the non-uniform electric field in different regions of the structure. In addition, a circuit model of the proposed structure is extracted, using carrier rate equations. Also, to achieve the optimum structure, it is tried to have trade-offs among thickness of the layers and have proper tuning of physical parameters. Eventually, frequency and transient response are investigated and it is shown that, in comparison with the previous conventional structure, significant improvements in gain-bandwidth product, speed and also in breakdown voltage are attained.展开更多
基金Supported by the State Key Project of Research and Development Plan of China under Grant No 2016YFB0400903the National Natural Science Foundation of China under Grant Nos 61634002,61274075 and 61474060+2 种基金the Key Project of Jiangsu Province under Grant No BE2016174the Anhui University Natural Science Research Project under Grant No KJ2015A153the Open Fund of State KeyLab of Optical Technologies on Nano-fabrication and Micro-engineering
文摘It is well known that -nitride semiconductors can generate the magnitude of MV/cm polarization electric field which is comparable with their ionization electric fields. To take full advantage of the polarization electric field, we design an N-face AlGaN solar-blind avalanche photodiode (APD) with an Al<sub>0.45</sub>Ga<sub>0.55</sub>N/Al<sub>0.3</sub>Ga<sub>0.7</sub>N heterostructure as separate absorption and multiplication (SAM) regions. The simulation results show that the N-face APDs are more beneficial to improving the avalanche gain and reducing the avalanche breakdown voltage compared with the Ga-face APDs due to the effect of the polarization electric field. Furthermore, the Al<sub>0.45</sub>Ga<sub>0.55</sub>N/Al<sub>0.3</sub>Ga<sub>0.7</sub>N heterostructure SAM regions used in APDs instead of homogeneous Al<sub>0.45</sub>Ga<sub>0.55</sub>N SAM structure can increase significantly avalanche gain because of the increased hole ionization coefficient by using the relatively low Al-content AlGaN in the multiplication region. Meanwhile, a quarter-wave AlGaN/AlN distributed Bragg reflector structure at the bottom of the device is designed to remain a solar-blind characteristic of the heterostructure SAM-APDs.
基金Project supported by the National Natural Science Foundation of China(Grant No.61505142)the Tianjin Natural Science Foundation(Grant No.16JCQNJC02100)
文摘For absorption linewidth inversion with wavelength modulation spectroscopy（WMS）, an optimized WMS spectral line fitting method was demonstrated to infer absorption linewidth effectively, and the analytical expressions for relationships between Lorentzian linewidth and the separations of first harmonic peak-to-valley and second harmonic zero-crossing were deduced. The transition of CO_2 centered at 4991.25 cm^（-1） was used to verify the optimized spectral fitting method and the analytical expressions. Results showed that the optimized spectra fitting method was able to infer absorption accurately and compute more than 10 times faster than the commonly used numerical fitting procedure. The second harmonic zero-crossing separation method calculated an even 6 orders faster than the spectra fitting without losing any accuracy for Lorentzian dominated cases. Additionally, linewidth calculated through second harmonic zero-crossing was preferred for much smaller error than the first harmonic peak-to-valley separation method. The presented analytical expressions can also be used in on-line optical sensing applications, electron paramagnetic resonance, and further theoretical characterization of absorption lineshape.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFB3608602)the Beijing Municipal Science and Technology Commission(Grant No.Z181100004418009)the National Natural Science Foundation of China(Grant No.61927806)。
文摘A Ga_(2)O_(3)/diamond separate absorption and multiplication avalanche photodiode(SAM-APD)with mesa structure has been proposed and simulated.The simulation is based on an optimized Ga_(2)O_(3)/diamond heterostructure TCAD physical model,which is revised by repeated comparison with the experimental data from the literature.Since both Ga_(2)O_(3)and diamond are ultra-wide bandgap semiconductor materials,the Ga_(2)O_(3)/diamond SAM-APD shows good solar-blind detection ability,and the corresponding cutoff wavelength is about 263 nm.The doping distribution and the electric field distribution of the SAM-APD are discussed,and the simulation results show that the gain of the designed device can reach 5×10^(4)and the peak responsivity can reach a value as high as 78 A/W.
基金supported by National Key Research&Development Program of China(2023YFB3809103 and 2023YFB3809100)National Natural Science Foundation of China(52201266,52171186)+1 种基金Startup Fund for Young Faculty at SJTU(SFYF at SJTU)Young Elite Scientists Sponsorship Program by CAST(2023QNRC001).
文摘Magnesium(Mg)is globally abundant in resources,and Mg‐based compounds—such as magnesium based hydrides,hydroxides,oxides,and magnesium metal‐organic frameworks(Mg MOFs)—have shown significant application prospects in gas separation.This is largely due to the electronic characteristics of Mg or Mg^(2+)ions,which facilitate the capture of hydrogen(H_(2))and acidic gases such as carbon dioxide(CO_(2))and sulfur dioxide(SO_(2))from other gases.Consequently,exploring the use of Mgbased materials in gas separation and purification applications could not only advance the scientific understanding of solid‐gas interaction mechanisms but also provide cost‐effective solutions for gas separation technology at an industrial level.This review summarizes the recent practices and explorations of Mg‐based solid‐state materials in various gas separation and purification methods,including physical adsorption‐based separation,chemical absorption‐based separation,and membrane‐based separation.For each separation method,the relevant Mg‐based materials are discussed in detail,and key findings from existing research are presented and analyzed.Additionally,inspired by the straightforward design of air‐stable hydrogen storage materials,this review specifically addresses anti‐passivation strategies for Mg‐based hydrides,which are crucial for their applications in hydrogen gas separation and purification.Finally,this review highlights key issues and fields for future research and development in Mg‐based gas separation materials.
文摘This paper presents a new method to increase the speed of the separated absorption, grading, charge, and multiplication avalanche photodiode （SAGCM-APD）. This improvement is obtained by adding a new thin charge layer between absorption and grading layers, with assuming the non-uniform electric field in different regions of the structure. In addition, a circuit model of the proposed structure is extracted, using carrier rate equations. Also, to achieve the optimum structure, it is tried to have trade-offs among thickness of the layers and have proper tuning of physical parameters. Eventually, frequency and transient response are investigated and it is shown that, in comparison with the previous conventional structure, significant improvements in gain-bandwidth product, speed and also in breakdown voltage are attained.
