| Summary: | 碩士 === 國立交通大學 === 電子工程學系 電子研究所 === 104 === It is known that micro cavities on enhance the absorption of a photodetector if certain resonant conditions are met. In this thesis we applied this idea to quantum dot infrared photodetectors (QDIPs) for long wavelength infrared detection. The microcavities were formed by thinning down the sample thickness to micron scale. The back metal and the surface metal gratings provide the necessary feedback for resonance.
By properly design the micro-cavity, we are able to match the resonant wavelength to our QDIPs’ absorption peak, which is at 8 m. The responsivities and the detectivities were both enhanced greatly compared with those without the microvities.
Compared with the reference structure (QDIPs without any cavity structure), the responsivity is enhanced by 35~60 times at different bias at 20K. Compared with the MCQDIPs structure which is non-resonant, the responsivity enhancement is about 18~30 times.
Even with the complicate process steps, the dark current of the devices with microcavities remained the same as those without microcavities. So the detectivities are also enhanced. The enhancement in detectivity of QDIPs with the full microcavity design is more than 10 times at 77K comparing with the devices without surface gratings.
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