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- Fu, Y, et al.
(författare)
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Photocurrents of 14 mu m quantum-well infrared photodetectors
- 2003
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 93:12, s. 9432-9436
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Tidskriftsartikel (refereegranskat)abstract
- We study the factors that determine photogenerated carriers and response wavelengths of photocurrents of long wavelength (similar to14 mum) quantum well (QW) infrared photodetectors (QWIPs). The material structures of QWIPs are first characterized by the photoluminescence measurements (PL). By calculating the density of photogenerated carriers in the continuum above the energy barriers using the PL calibrated QWIP structures, we have demonstrated that due to the sample quality, the photocarriers can be either in miniband states (Bloch states in the multiple quantum wells), or they transport from one quantum well to the next in the form of running waves. By including possible scattering processes at the QWIP working temperature to link the theoretically calculated photocarrier density with the experimentally measured photocurrent, it is shown that the width of the photocurrent peaks of 14 mum GaAs/AlGaAs QWIPs under investigation is determined by the optical phonon emissions of photocarriers. We have further calculated the densities of photocarriers in the QWIPs reported in the literature. It is shown that the Bloch wave boundary conditions are appropriate for QWIPs with narrow QWs, whereas running wave boundary conditions are appropriate for wide QWs.
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| 2. |
- Fu, Y, et al.
(författare)
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Quantum mechanical model and simulation of GaAs/AlGaAs quantum well infrared photodetector-I optical aspects
- 2002
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Ingår i: Hongwai yu haomibo xuebao. - : Science Press. - 1001-9014. ; 21:5, s. 321-326
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Tidskriftsartikel (refereegranskat)abstract
- A complete quantum mechanical model for GaAs/AlGaAs quantum well infrared photodetectors(QWIPs) is presented here. The model consisted of four parts: (1) Starting with the description of the electromagnetic field of the infrared radiation in the QWIP, effective component of the vector potential [\A(z)\] along the QWIP growth direction (z-axis) due to the optical diffraction grating was calculated. (2) From the wave transmissions and the occupations of the electronic states, it was discussed that the dark current in the QWIP is determined by the drift-diffusion current of carriers thermally excited from the ground sublevel in the quantum well to extended states above the barrier. (3) The photocurrent was investigated by the optical transition (absorption coefficient between the ground state to excited states due to the nonzero-[\A(z)\]). (4) By studying the inter-diffusion of the At atoms across the GaAs/AlGaAs heterointerfaces, the mobility of the drift-diffusion carriers in the excited states was calculated, so the measurement results of the dark current and photocurrent spectra can be explained theoretically. With the complete quantum mechanical descriptions of (1-4), QWIP device design and optimization are possible.
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