The application of a modified Levine model to quantum-well infrared photodetectors in the low-temperature regime
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The application of a modified Levine model to quantum‑well infrared photodetectors in the low‑temperature regime Anibal Thiago Bezerra1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A different approach to the calculation of the dark current of quantum-well infrared photodetectors (QWIPs) based on a modified version of Levine’s method is presented. A quantum-well-dependent transmission probability is proposed and evaluated. The results show that the model accurately reproduces the experimental behavior of the photodetector dark current in the low-temperature regime. As a proof of concept, the presented approach is applied to elucidate the role of filter barriers in QWIP structures. As expected, a significant decrease in the dark current is observed, principally in the high bias regime, demonstrating that the modified Levine’s model captures relevant information about the behavior of the dark current of photovoltaic devices. Keywords Dark current · Quantum-well infrared photodetectors · Levine model · Filter barriers
1 Introduction The dark current is an unwanted effect that originates from processes unrelated to optical excitation, representing one of the major factors limiting the operation of photovoltaic devices such as photodetectors [1–3]. It actively contributes to the noise in such devices and reduces their operating temperature. Therefore, understanding the mechanisms underlying the dark current is crucial to their design and optimization [4]. Specifically, when dealing with infrared photodetectors based on quantum wells, also called quantum-well infrared photodetectors (QWIPs), the origins of the dark current are mainly related to three processes [1, 5]: thermionic emission, temperature-assisted tunneling, and sequential tunneling. Thermionic emission is a noncoherent process characterized by thermal excitation processes and is predominant at high temperatures. Meanwhile, temperature-assisted tunneling is a process characterized by thermal excitation followed by carriers tunneling through the triangular barriers generated by the built-in electric field or that applied to the structure. Finally, sequential tunneling is a process characterized by * Anibal Thiago Bezerra anibal.bezerra@unifal‑mg.edu.br 1
tunneling of carriers through the structure generating the current. The latter is dominant at low temperatures. Among the most widely accepted models for describing the dark current in QWIPs, the simplest and most widely used is the capture and emission process that considers trapping processes to balance the emission or escape of charge carriers from the quantum wells within the device [1]. In such a thermodynamic model, the dark current is given by [2] −
Id ∼ e
Eb −EF kB T
(1)
,
where T is the device temperature, kB is the Boltzmann constant, and Eb is the energy difference between the bound state in the quantum well and the top of the barrier, defining the minimum energy needed to remove carriers thermally from the well [2]. As the electron gas in the well is n
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