A complete quantum mechanical model for GaAs/AlGaAs quantum well infrared photodetectors(QWIPs) was presented. The photocurrent was investigated by the optical transition(absorption coefficient)between the ground stat...A complete quantum mechanical model for GaAs/AlGaAs quantum well infrared photodetectors(QWIPs) was presented. The photocurrent was investigated by the optical transition(absorption coefficient)between the ground state and the excited states due to the nonzero component of the radiation field along the sample growth direction. By studying the inter diffusion of the Al atoms across the GaAs/AlGaAs heterointer faces, the mobility of the drift diffusion carriers in the excited states was calculated. As a result, the measurement results of the dark current and the photocurrent spectra are explained theoretically.展开更多
Ferroelectricity in Langmuir-Blodgett (LB) films (Z-type and alternated Y-type) of nitrogencrown (NC) and arachidic acid (AA) was investigated by electric polarization measurements and surface pressure-molecular area ...Ferroelectricity in Langmuir-Blodgett (LB) films (Z-type and alternated Y-type) of nitrogencrown (NC) and arachidic acid (AA) was investigated by electric polarization measurements and surface pressure-molecular area (p-A) isotherm. For Z-type AA LB multilayer and the AA LB films incorporating barium and manganese ions, as well as for Z-type NC LB multilayer and the Y-type NC/AA alternating LB films, typical hysteresis loops of the samples were observed and confirmed existence of the remnant polarizations in the LB films. Their corresponding remnant polarizations were found to be 15, 180, 650, 450 and 9400 mC·m-2, respectively. Therefore, it was demonstrated that the enhancement of ferroelectricity in the LB films could be created by incorporation of barium and manganese ions into the LB film structures and strong interaction between alternating monolayers of the samples. These novel approaches can be employed to create strong ferroelectric LB films to make ferroelectric thin-film device for practical applications.展开更多
文摘A complete quantum mechanical model for GaAs/AlGaAs quantum well infrared photodetectors(QWIPs) was presented. The photocurrent was investigated by the optical transition(absorption coefficient)between the ground state and the excited states due to the nonzero component of the radiation field along the sample growth direction. By studying the inter diffusion of the Al atoms across the GaAs/AlGaAs heterointer faces, the mobility of the drift diffusion carriers in the excited states was calculated. As a result, the measurement results of the dark current and the photocurrent spectra are explained theoretically.
基金supported by the National Natural Science Foundation of China(Grant Nos.10274014 and 19704004)the Overseas Student Foundation of the Ministry of Education of Chinathe Education Development Foundation by Shanghai City and the Education Commission of Shanghai City,as well as the opening topic supported by National Laboratory for Infrared Physics of the Chinese Academy of Scieaces.
文摘Ferroelectricity in Langmuir-Blodgett (LB) films (Z-type and alternated Y-type) of nitrogencrown (NC) and arachidic acid (AA) was investigated by electric polarization measurements and surface pressure-molecular area (p-A) isotherm. For Z-type AA LB multilayer and the AA LB films incorporating barium and manganese ions, as well as for Z-type NC LB multilayer and the Y-type NC/AA alternating LB films, typical hysteresis loops of the samples were observed and confirmed existence of the remnant polarizations in the LB films. Their corresponding remnant polarizations were found to be 15, 180, 650, 450 and 9400 mC·m-2, respectively. Therefore, it was demonstrated that the enhancement of ferroelectricity in the LB films could be created by incorporation of barium and manganese ions into the LB film structures and strong interaction between alternating monolayers of the samples. These novel approaches can be employed to create strong ferroelectric LB films to make ferroelectric thin-film device for practical applications.
