We designed two transmission-mode GaAs/AIGaAs photocathodes with different AlxGa1-xAs layers, one has an AlxGal-xAs layer with the Al component ranging from 0.9 to 0, and the other has a fixed AI component 0.7. Using ...We designed two transmission-mode GaAs/AIGaAs photocathodes with different AlxGa1-xAs layers, one has an AlxGal-xAs layer with the Al component ranging from 0.9 to 0, and the other has a fixed AI component 0.7. Using the first-principle method, we calculated the electronic structure and absorption spectrum ofAlx Ga1-x As at x = 0, 0.25, 0.5, 0.75 and 1, calculation results suggest that with the increase of the A1 component, the band gap of AlxGa1-xAs increases. Then we activated the two samples, and obtained the spectral response curves and quantum efficiency curves; it is found that sample 1 has a better shortwave response and higher quantum efficiency at short wavelengths. Combined with the band structure diagram of the transmission-mode GaAs/AIGaAs photo- cathode and the fitted performance parameters, we analyze the phenomenon. It is found that the transmission-mode GaAs/AlGaAs photocathode with variable AI component and various doping structure can form a two-stage built-in electric field, which improves the probability of shortwave response photoelectrons escaping to the vacuum. In con- clusion, such a structure reduces the influence of back-interface recombination, improves the shortwave response of the transmission-mode photocathode.展开更多
Simulation studies are carried out on the large signal and noise properties of heterojunction（HT）Al_xGa_（1-x）As/GaAs double drift region（DDR） IMPATT devices at V-band（60 GHz）.The dependence of Al mole fraction...Simulation studies are carried out on the large signal and noise properties of heterojunction（HT）Al_xGa_（1-x）As/GaAs double drift region（DDR） IMPATT devices at V-band（60 GHz）.The dependence of Al mole fraction on the aforementioned properties of the device has been investigated.A full simulation software package has been indigenously developed for this purpose.The large signal simulation is based on a non-sinusoidal voltage excitation model.Three mole fractions of Al and two complementary HT DDR structures for each mole fraction i.e.,six DDR structures are considered in this study.The purpose is to discover the most suitable structure and corresponding mole fraction at which high power,high efficiency and low noise are obtained from the device.The noise spectral density and noise measure of all six HT DDR structures are obtained from a noise model and simulation method.Similar studies are carried out on homojunction（HM） DDR GaAs IMPATTs at 60 GHz to compare their RF properties with those of HT DDR devices.The results show that the HT DDR device based on N-Al_xGa_（1-x）As/p-GaAs with 30%mole fraction of Al is the best one so far as large signal power output,DC to RF conversion efficiency and noise level are concerned.展开更多
基金supported by the National Natural Science Foundation of China(Nos.91433108,61301023)
文摘We designed two transmission-mode GaAs/AIGaAs photocathodes with different AlxGa1-xAs layers, one has an AlxGal-xAs layer with the Al component ranging from 0.9 to 0, and the other has a fixed AI component 0.7. Using the first-principle method, we calculated the electronic structure and absorption spectrum ofAlx Ga1-x As at x = 0, 0.25, 0.5, 0.75 and 1, calculation results suggest that with the increase of the A1 component, the band gap of AlxGa1-xAs increases. Then we activated the two samples, and obtained the spectral response curves and quantum efficiency curves; it is found that sample 1 has a better shortwave response and higher quantum efficiency at short wavelengths. Combined with the band structure diagram of the transmission-mode GaAs/AIGaAs photo- cathode and the fitted performance parameters, we analyze the phenomenon. It is found that the transmission-mode GaAs/AlGaAs photocathode with variable AI component and various doping structure can form a two-stage built-in electric field, which improves the probability of shortwave response photoelectrons escaping to the vacuum. In con- clusion, such a structure reduces the influence of back-interface recombination, improves the shortwave response of the transmission-mode photocathode.
文摘Simulation studies are carried out on the large signal and noise properties of heterojunction（HT）Al_xGa_（1-x）As/GaAs double drift region（DDR） IMPATT devices at V-band（60 GHz）.The dependence of Al mole fraction on the aforementioned properties of the device has been investigated.A full simulation software package has been indigenously developed for this purpose.The large signal simulation is based on a non-sinusoidal voltage excitation model.Three mole fractions of Al and two complementary HT DDR structures for each mole fraction i.e.,six DDR structures are considered in this study.The purpose is to discover the most suitable structure and corresponding mole fraction at which high power,high efficiency and low noise are obtained from the device.The noise spectral density and noise measure of all six HT DDR structures are obtained from a noise model and simulation method.Similar studies are carried out on homojunction（HM） DDR GaAs IMPATTs at 60 GHz to compare their RF properties with those of HT DDR devices.The results show that the HT DDR device based on N-Al_xGa_（1-x）As/p-GaAs with 30%mole fraction of Al is the best one so far as large signal power output,DC to RF conversion efficiency and noise level are concerned.
