| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 101 === The electrical and optical properties of 2.34ML、3.3ML quantum dots (QDs) samples and GaAs bulk sample are studied using the photo-capacitance measurements. First of all, we discuss the mechanism of the photo-capacitance illuminated by near-infrared light source. Secondly, according to the photo-capacitance measurements, the deep level traps near 1.3eV exist in both QDs-samples and GaAs bulk sample. In order to investigate how the QDs contribute the photo-capacitance, we measured the 3.3ML QDs-sample with better carrier confinement. The photo-capacitance of 3.3 ML QDs-sample is observed if the illuminating energy is larger than the ground state of the QDs. Therefore, the quantum structure can enhance the photo-capacitance indeed. In addition, if we change the sweeping rate of bias in the C-V measurements, the photo-capacitance in the QDs plateau can be modulated. It means that the photo-capacitance near the plateau of the QDs is related to defects with slow time constant. We establish a model to explain the interaction between the deep level traps and the QDs, and the photo-capacitance is simulated based on the QDs and deep level traps respectively. In summary, the photo-capacitance is caused by the QDs and the deep level traps of 1.3 eV.
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