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Comparison of Quantum Dots-in-a-Double-Well and Quantum Dots-in-a-Well Focal Plane Arrays in the Long-Wave Infrared | IEEE Journals & Magazine | IEEE Xplore

Comparison of Quantum Dots-in-a-Double-Well and Quantum Dots-in-a-Well Focal Plane Arrays in the Long-Wave Infrared


Abstract:

Our previous research has reported on the development of the first generation of quantum dots-in-a-well (DWELL) focal plane arrays (FPAs), which are based on InAs quantum...Show More

Abstract:

Our previous research has reported on the development of the first generation of quantum dots-in-a-well (DWELL) focal plane arrays (FPAs), which are based on InAs quantum dots (QDs) embedded in an InGaAs well having GaAs barriers, which have demonstrated spectral tunability via an externally applied bias voltage. More recently, technologies in DWELL devices have been further advanced by embedding InAs QDs in InGaAs and GaAs double wells with AlGaAs barriers, leading to a less strained InAs/InGaAs/GaAs/AlGaAs heterostructure. These lower strain quantum dots-in-a-double-well devices exhibit lower dark current than the previous generation DWELL devices while still demonstrating spectral tunability. This paper compares two different configurations of double DWELL (DDWELL) FPAs to a previous generation DWELL detector and to a commercially available quantum well infrared photodetector (QWIP). All four devices are 320 × 256 pixel FPAs that have been fabricated and hybridized with an Indigo 9705 read-out integrated circuit. Radiometric characterization, average array responsivity, array uniformity and measured noise equivalent temperature difference for all four devices is computed and compared at 60 K. Overall, the DDWELL devices had lower noise equivalent temperature difference and higher uniformity than the first-generation DWELL devices, although the commercially available QWIP has demonstrated the best performance.
Published in: IEEE Transactions on Electron Devices ( Volume: 58, Issue: 7, July 2011)
Page(s): 2022 - 2027
Date of Publication: 02 May 2011

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I. Introduction

Infrared focal plane arrays (FPAs) are useful for thermal imaging, night vision, satellite imaging, distance ranging, and improvised explosive device detection in both military and commercial applications [1]–[4]. There are more established technologies in both HgCdTe [5] and band-gap-engineered quantum well (QW) infrared photodetectors (QWIPs) that have produced FPAs capable of sensing and measurement across most of the infrared spectrum from midwave to very long wave with low noise [1], [6]–[8]. Many of these devices are well characterized and have demonstrated adequate performance in the applications above. However, adding spectral tunability to these sensors expands their potential applications and suitability for each application. Several papers have reported on the characterization of a hybrid device between QWIPs and the quantum dot (QD) infrared protectors (QDIPs), which is called the dot-in-a-well (DWELL) [9]–[14] device that exhibits this tunability. Although not as well developed as the established QWIP devices, these DWELL structure include advantages such as multispectral response with a bias-dependent spectral tunability and reproducible control of the operating wavelength like a QWIP and the low dark current and normal incidence operation of a QDIP [11]. The multispectral response is a result of multiple transition energies (dot to dot, dot to well, or dot to continuum), and the spectral tunability is a result from band bending with applied bias voltage changing the transition energies [9]–[11]. More recently, the DWELL structure has been modified by embedding QDs in a QW structure and then embedding this hybrid structure within another QW, which is called a double DWELL or DDWELL [12] in this paper. This new structure has the advantage of lower strain in the heterostructure, which leads to higher temperature operation while maintaining low dark current. The remainder of this paper compares the original DWELL FPA and two versions of the new DDWELL FPAs to a commercially available QWIP FPA. A previous work on characterization of the DDWELL was from an intermediate structure only. This paper elaborates with further characterization of that intermediate DDWELL, expands with characterization of the newer complete DDWELL, and compares them to the original DWELL device and the well-established QWIP [14]. Although the QWIP device demonstrates the best performance and lowest noise, the second generation of DDWELL detectors have dramatically increased performance over the first generation and have the added benefit of spectral tunability [11], which many established infrared (IR) FPA technologies lack.

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