Design and performance of dual-band MWIR/LWIR focal plane arrays based on a type-II superlattice nBn structure

Abstract

Dual-band infrared detector, which acquires more image information than single-band detectors, has excellent detection, recognition, and identification capabilities. The dual-band detector can have two bumps to connect with each absorber layer, but it is difficult to implement small pitch focal plane arrays and its fabrication process is complicated. Therefore, the most effective way for a dual-band detector is to acquire each band by biasselectable with one bump. To aim this, a dual-band MWIR/LWIR detector based on an InAs/GaSb type-II superlattice nBn structure was designed and its performance was evaluated in this work. Since two absorber layers were separated by the barrier layer, each band can be detected by bias-selectable with one bump. The fabricated dual-band device exhibited the dark current and spectral response characteristics of MWIR and LWIR bands under negative and positive bias, respectively. Spectral crosstalk that is a major issue in dualband detectors was also improved. Finally, a 20 m pitch 640  512 dual-band detector was fabricated, and both MWIR and LWIR images exhibited an average noise equivalent temperature difference of 30 mK or less at 80 K.

Independently Accessible Dual-Band Barrier Infrared Detector Using Type-II Superlattices

“…As shown in Figure 6, the dark current of the BC is almost flat up to the reverse bias of −1 V, while that of the RC slightly increases with increasing reverse bias up to −1 V. The dark currents of the BC and RC are 1.56 × 10 −7 and 3.01 × 10 −6 A/cm 2 at a reverse bias of V = −0.2 V, respectively. These values are comparable with the recent published experimental results, approximately 4 × 10 −8 and 4 × 10 −6 A/cm 2 at V = −0.2 V, at 80 K, respectively, in an NBn dual-band IR detector [28]. Considering also that the theoretically estimated dark current density of T2SL InAs/GaSb nBn at 77 K is less than 10 −9 A/cm 2 for λ c = 5 µm and 10 −6 A/cm 2 for λ c = 10 µm, respectively [32], the dark current of DBIRD seems to be as good as from a well-passivated T2SL InAs/GaSb single-band nBn device.…”

“…Figure 3 shows schematic diagrams of the selected processing steps. Recent papers describing the device processing of T2SL infrared detectors include references [25][26][27][28].…”

640 x 512 dual-band midwave and longwave infrared focal plane array at i3system

“…wafer based on InAs/GaSb T2SL nBn structure for dual-band MWIR/LWIR FPA was designed using eight band k•p numerical method reported in previous study (design details are listed in Table 1). The bandgap energies of the barrier, MWIR and LWIR layers were ~0.544 eV, ~0.249 eV and ~0.134 eV, respectively [13]. Each epi.…”

“…layer was sequentially grown on a Te-doped 3-inch GaSb substrate by molecular beam epitaxy (MBE) as shown in Table 1. The MWIR absorber layer was grown earlier and thicker than LWIR absorber to minimize a spectral crossover when infrared is incident on the backside of the dual-band FPA [13]. The dual-band MWIR/LWIR FPA was fabricated following the process sequence of the InAs/GaSb LWIR nBn devices reported in previous studies [13,14,15,16,17]: dry-etch for pixel isolation, post-treament, passivation film deposition, electrode area etching, and metallization.…”

“…The MWIR absorber layer was grown earlier and thicker than LWIR absorber to minimize a spectral crossover when infrared is incident on the backside of the dual-band FPA [13]. The dual-band MWIR/LWIR FPA was fabricated following the process sequence of the InAs/GaSb LWIR nBn devices reported in previous studies [13,14,15,16,17]: dry-etch for pixel isolation, post-treament, passivation film deposition, electrode area etching, and metallization. However, the dual-band nBn device should be dry-etched more deeply than the single-band nBn device for pixel isolation because of the thicker absorber layer including MWIR and LWIR absorbers.…”