Improving the operation temperature of the focal plane array (FPA) imagers is critical in meeting the demands to reduce the size, weight, and power (SWaP) for mid-infrared detection systems. In this work, we report the demonstration of a 15 µm-pitch 640×512 middle-format pBn FPA device with a 50% cutoff wavelength of 4.8 µm based on short period of InAs/InAsSb-based “Ga-free” type-II strained-layer superlattices, which achieves a high operating temperature (HOT) reaching 185 K. The pBn FPA exhibits a mean noise equivalent differential temperature (NETD) of 39.5 mK and an operability of 99.6% by using f/2.0 optics for a 300 K background at 150 K. The mean quantum efficiency is 57.6% without antireflection coating and dark current density is 5.39×10−5 A/cm2 at an operation bias of −400 mV, by which the mean specific detectivity(D*) is calculated as high as 4.43×1011 cm.Hz½/W.

We report on a mid wavelength (MW) type II InAs/GaSb superlattice (SL) photodetector structure using SiO x N y as the passivation material. The 50% cutoff wavelength of the photoresponse is 4.8 µm at 77 K. R 0 A, the resistance-and-area product at zero bias, is 2.1×103 Ω·cm2 for the device with the SiO x N y passivation, which is about 13 times larger than that without the passivation. Our result indicates SiO x N y passivation is an effective way to reduce the shunt current for MW InAs/GaSb SL photodetector.

Ga-free InAs/InAsSb type-II superlattices (T2SLs) are emerging as candidate materials for high temperature operation of mid-infrared photodetectors, which are critical for infrared technology with an aim to provide low-cost and compact detection systems. In this work, by utilizing upside-down device structure, a closely lattice-matched Al0.83Ga0.17AsSb quaternary alloy as electron barrier was pre-grown before the growth of InAs/InAsSb T2SLs absorber in a nBn device. Based on this design, we have demonstrated 5-µm cut-off mid-wavelength infrared (MWIR) photodetectors that exhibited a dark current density of 1.55 × 10−4 A/cm2 at an operation bias 400mV at 150K. A saturated quantum efficiency at ∼4.0 µm reaches 37.5% with a 2 µm absorber and the peak responsivity reaches 1.2 A/W, which yields a peak specific detectivity as high as ∼1.82 × 1011 cm·H z1/2/W at a forward bias of 400mV.

In this work, by utilizing a band-aligned AlAs0.08Sb0.92/AlSb-based unipolar compound barrier design, a high-operability (∼99.7%) InAsSb bulk absorber-based mid-wavelength infrared 640 × 512 focal plane array (with a 50% cut-off wavelength at 4.1 μm at 150 K) exhibiting distinct infrared images from 150 K up to 205 K has been achieved, which suggests great potential for high operation temperature detection applications. At 150 K and −400 mV bias, the photodetectors exhibit a low dark current density of ∼3.9 × 10−6 A∕cm2, a quantum efficiency of 65.1% at peak responsivity (∼3.8 μm), and a specific detectivity of 1.73 × 1012 Jones. From 150 to 185 K, the focal plane array exhibits ∼30.2 mK and ∼69.5 mK noise equivalent temperature difference values by using f/2.0 optics and 6.45 ms and 0.61 ms integration times, respectively.

Versatile applications have driven a desire for dual-band detection that enables seeing objects in multiple wavebands through a single photodetector. In this paper, a concept of using graphene/p-GaN Schottky heterojunction on top of a regular AlGaN-based p-i-n mesa photodiode is reported for achieving solar-/visible-blind dual-band (275 nm and 365 nm) ultraviolet photodetector with high performance. The highly transparent graphene in the front side and the polished sapphire substrate at the back side allows both top illumination and back illumination for the dual band detection. A system limit dark current of 1×10−9 A/cm2 at a negative bias voltage up to -10 V has been achieved, while the maximum detectivity obtained from the detection wavebands of interests at 275 nm and 365 nm are ∼ 9.0 ×1012 cm·Hz1/2/W at -7.5 V and ∼8.0 × 1011 cm·Hz1/2/W at +10 V, respectively. Interestingly, this new type of photodetector is dual-functional, capable of working as either photodiode or photoconductor, when switched by simply adjusting the regimes of bias voltage applied on the devices. By selecting proper bias, the device operation mode would switch between a high-speed photodiode and a high-gain photoconductor. The device exhibits a minimum rise time of ∼210 µs when working as a photodiode and a maximum responsivity of 300 A/W at 6 μW/cm2 when working as a photoconductor. This dual band and multi-functional design would greatly extend the utility of detectors based on nitrides.