## Abstract

In this paper, we proposed a new design of infrared photodetector structure based on ring-shaped multiple quantum wells for long-infrared and far-infrared (FIR) regimes. The absorption coefficient of the proposed photodetector that consists of $\mathrm{GaAs}/{\mathrm{Al}}_{0.25}{\mathrm{Ga}}_{0.75}\mathrm{As}$ quantum wells with a thickness of 4 nm and a barrier of 40 nm has been calculated, from which a dominant peak of 50 um locates in the FIR regime. The proposed device has a planar structure with small thickness compared with ordinary rectangular multiple quantum well photodetectors. Also, there is 100% enhancement in typical IR absorption versus these ordinary photodetectors. Electronic states and wave functions calculated through solving the Schrödinger equation and then the effect of quantum well number on important parameters of photodetectors, such as gain mode and dark current, are investigated. According to the results, dark current decreases 1 order of magnitude when the number of quantum wells increases from 3 to 4. Also, absorption has redshift and simultaneously increases.

© 2019 Optical Society of America

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