| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 103 === In this study, we analyze the transient current and transient capacitance measurement of the N=2.7% 80 Å GaAsN/GaAs quantum well (QW) samples grown by MBE, and discuss the dynamic processes of carrier storage in QW for the change of light situation. At the moment of light-on suddenly, the QW is charging by the photocurrent, and a potential drop of charged QW is producing. So the measured capacitance of depletion increases with the potential drop of charged QW. By contrast, the QW is discharging at the situation of light-off, and the measured capacitance of depletion decreases with time. However, we can’t detect the charging process of QW for the as-grown sample in the transient measurements. The optical properties of as-grown sample are studied by photoluminescence (PL). An additional peak (1.03 eV) can be observed, which is due to the recombination between the deep level defect and QW. Most of electron-hole pairs in QW will recombine with deep level. Therefore, the as-grown QW behaves poor carrier confinement. Rapid thermal annealing (RTA) can reduce point defect effectively and enhance the carrier confinement ability in QW. In some case of light-off, the measured capacitance of depletion behaves a persistent capacitance phenomenon. The persistent capacitance is caused by that some carriers are still confined in QW after light-off, and the amount of stored carriers can be controlled by applied reverse bias. This mechanism of written by light and erased by reverse bias provides an idea for optical memory device.
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