| Summary: | 碩士 === 國立臺灣大學 === 生醫電子與資訊學研究所 === 105 === Quantum wells Infrared photodetector have been widely used in many fields, such as astronomy, medical, construction, military, security systems and etc. In our study, superlattice structure is added in order to enhance light absorption efficiency. Grating structure can also improve responsivity.
The effect of grating system not only can concentrate light energy and then improve the photocurrent, but also can greatly increase its absorption in the active layer. Superlattice structure can help electrons easily excited by photons, which make our device can be operated at low bias voltage. Due to the small resistance, the dark current can be effectively reduced and then reduce the noise generation. Another study is to enhance responsivity of the photo detector by changing grating depth.
We find that as the period of grating structure is fixed at 2μm, the relationship between the grating depth and the responsivity is not an increasing function. According to the results, the optimal value of the responsivity is detected when the grating depth is 1.3 μm. Compared with the devices without the grating structure, our best device had 2.5 times of the gain. The maximum operation temperature of our best device is measured at 83K.
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