High performance 15-μm pitch 640 × 512 MWIR InAs/GaSb type-II superlattice sensors

Abstract

We report the high performance of Mid-wave Infrared Region (MWIR) InAs/GaSb Type-II Superlattice (T2SL) sensors with $640\times512$ format and 15- $\mu \text{m}$ pixel pitch at both Focal Plane Array (FPA) and pixel level. The p-intrinsic-Barrier-n epilayer structure is adopted for this study, which is grown on 620 ± $30~ \mu \text{m}$ thick GaSb substrate and highly-doped GaSb cap layer at the top structure. The mesa type pixels with sizes of $220\,\,\mu \text{m}\,\,\times 220\,\,\mu \text{m}$ have dark currents $7.8\times10$ −12 A at 77 K both of which are equivalent to state-of-the-art values for Type-II Superlattice sensors. The various passivation techniques to lower the dark current are applied and the results are given in terms of dark current. Electro-optical measurements yielded comparable results to literature. After gathering data and optimizing the fabrication conditions, the FPA of 15- $\mu \text{m}$ pitch having $4.92~ \mu \text{m}$ cut-off wavelength ( $\lambda _{\mathrm {c}}$ ) shows 1.6 A/W peak responsivity, Noise Equivalent Temperature Difference (NETD) of 22.6 mK with optics of f/2.3, quantum efficiency larger than 65% and 99.75% operability. The acquired images by using aforementioned FPA device is presented in this paper. With the reduction of dark current, an encouraging imaging performance is obtained which shows the potential of the Type-II Superlattice detectors in 3 rd generation infrared sensors.