Mid-infrared quantum dot barrier photodetectors with extended cutoff wavelengths

Abstract

A method to extend the cutoff wavelength of mid-infrared barrier photodetectors by incorporating self-assembled InSb quantum dots into the active area of the detector is demonstrated. This approach enables the extension of the cutoff wavelength of barrier photodetectors from 4.2 to 6 mm, demonstrating infrared response at temperatures up to 225 K.Introduction: Recently, a new class of infrared (IR) detectors, the so-called nBn or XBn barrier photodetectors, has been proposed and demonstrated [1][2][3]. These detectors utilise a wide bandgap barrier layer sandwiched between the top contact and the absorber layers. The barrier blocks the flow of majority carriers (electrons), but not minority carriers. The barrier photodetector architecture offers advantages of reduced dark current resulting from suppressed Shockley-Read-Hall (SRH) recombination process [4] and of planar processing. This simplifies fabrication in that it no longer requires etching through the absorption layer and obviates the need for post-etch passivation. However, the barrier photodetectors' implementation is currently limited by the available choice of barrier and absorber materials that must have the appropriate band alignment and be lattice-matched to a suitable substrate. So far, high-performance barrier photodetectors with an InAsSb/ AlAsSb absorber -barrier combination have been demonstrated with cutoff wavelengths limited to about l ¼ 4 mm [3]. Here, we demonstrate an approach to extend the wavelength of barrier photodetectors by incorporating nanostructures into the absorber of these devices. The barrier photodetectors with self-assembled quantum dots (QDs) integrated into InAs 0.91 Sb 0.09 exhibited cutoff wavelength exceeding l ¼ 6 mm and operated above T ¼ 225 K. This development expands the potential application areas of barrier photodetectors and enables a new class of devices with appealing physical properties.

Carrier transport in unipolar barrier infrared detectors

“…However, an imperfect barrier would also block minority carriers, resulting in higher than expected turn-on bias, as has been observed experimentally in both MWIR and LWIR devices [10,12,21]. Minority carrier blocking can be caused by (1) barrier doping, and/or (2) un-intended band offset between the barrier and the absorber.…”

“…Figure 1 shows the spectral response from a quantum dot barrier infrared detector (QD-BIRD). The device architecture is the same as the standard InAsSb-AlAsSb nBn structure as originally described by Maimon and Wicks [3], except that the absorber region contains periodic inserts of quantum dot layers to extend the cutoff wavelength [21]. Detailed description of the device structure and performance has been reported elsewhere [21,22].…”

Theoretical Aspects of Minority Carrier Extraction in Unipolar Barrier Infrared Detectors

“…However, an imperfect barrier would also block minority carriers, resulting in higher than expected turn-on bias, as has been observed experimentally for both MWIR and LWIR devices. 10,12,21 Minority carrier blocking can be caused by: 1 barrier doping, and/or 2 unintended band offset between the barrier and the absorber.…”

Spectral selectivity of subwavelength gold-based photonic crystals on GaAs substrate

“…The neverending struggle for fabricating more efficient photodetectors is one of the most attractive subjects in the field [1]. Many bottom up approaches have been explored to improve the performance of the photodetectors using novel material and device fabrication techniques [2]. As these new technologies become more advanced and expensive, top-down approaches to improve current generation photodetectors have become of interest.…”