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This work investigates the potential of InAs/GaSb superlattice detectors for the shortwavelength infrared spectral band. A barrier detector structure was grown by molecular beam epitaxy and devices were fabricated using standard photolithography techniques. Optical and electrical characterisations were carried out and the current limitations were identified. The authors found that the short diffusion length of ~1.8 μm is currently limiting the quantum efficiency (double-pass, no anti-reflection coating) to 43% at 2.8 μm and 200 K. The dark current density is limited by the surface leakage current which shows generation-recombination and diffusion characters below and above 195 K, respectively. By fitting the size dependence of the dark current, the bulk values have been estimated to be 6.57·10-6 A/cm² at 200 K and 2.31·10-6 A/cm² at 250 K, which is only a factor of 4 and 2, respectively, above the Rule07. [ABSTRACT FROM AUTHOR]

This work investigates the potential of p-type InAs/GaSb superlattice for the fabrication of full mid-wave megapixel detectors with n-on-p polarity. A significantly higher surface leakage is observed in deep-etched n-on-p photodiodes compared to p-on-n diodes. Shallowetch and two-etch-step pixel geometry are demonstrated to mitigate the surface leakage on devices down to 10 µm with n-on-p polarity. A lateral diffusion length of 16 µm is extracted from the shallow etched pixels, which indicates that cross talk could be a major problem in small pitch arrays. Therefore, the two-etch-step process is used in the fabrication of 1280 × 1024 arrays with a 7.5 µm pitch, and a potential operating temperature up to 100 K is demonstrated. [ABSTRACT FROM AUTHOR]

Herein, results from noise and dark current density studies on InAs/GaSb type‐II superlattice IR detectors are presented. The activation energy of the dark current density is used to identify the dominating dark current mechanisms (generation–recombination (GR), tunneling, or diffusion dark current) as a function of temperature and bias. The bias evolution of the power spectral density (PSD) is measured in dark conditions for several temperatures. At the operating bias of the detectors, the arrays show a white noise–dominated spectrum up to 100 K with a minor 1/f contribution (corner frequency around 10 Hz), while for higher temperatures the spectra are 1/f dominated. The 1/f noise component is compared to the dominating dark current mechanism in the same temperature and bias regimes. A strong correlation between the 1/f noise component and the dominating dark current (I) is found, with the PSD proportional to I for tunneling currents and I2 for GR and diffusion currents. Very low noise coefficients of αGR = 4.8 × 10−9 Hz−1, αdiff = 1.9 × 10−10 Hz−1, and αtun = 2.1 × 10−16 A Hz−1 are observed for these detectors. [ABSTRACT FROM AUTHOR]

We analyze and compare different aspects of InAs/InAsSb and InAs/GaSb type-II superlattices for infrared detector applications and argue that the former is the most effective when implemented for mid-wavelength infrared detectors. We then report results on an InAs/InAsSb superlattice based mid-wavelength high operating temperature barrier infrared detector. At 150 K, the 50% cutoff wavelength is 5.37 μm, the quantum efficiency at 4.5 μm is ∼52% without anti-reflection coating, the dark current density under −0.2 V bias is 4.5 × 10−5 A/cm2, and the dark-current-limited and the f/2 black-body (300 K background in 3–5 μm band) specific detectivities are 4.6 × 1011 and 3.0 × 1011 cm-Hz1/2/W, respectively. A focal plane array made from the same material exhibits a mean noise equivalent differential temperature of 18.7 mK at 160 K operating temperature with an f/2 optics and a 300 K background, demonstrating significantly higher operating temperature than InSb. [ABSTRACT FROM AUTHOR]

We have examined, theoretically, minority carrier collection in unipolar barrier infrared photodetectors. In barrier infrared detectors, for example the nBn, the unipolar barrier should block only majority carriers and allow unimpeded flow of minority carriers. However, an imperfect barrier would also block minority carriers, resulting in higher than expected turn-on bias. Minority carrier blocking can be caused by barrier doping or unintended band offset between the barrier and the absorber. The distinct manner in which these two mechanisms affect device performance were investigated. We found that introduction of an appropriate amount of barrier doping can reduce depletion dark current without increasing turn-on bias. We examined the effects of band structure on conductivity effective masses when the n-type absorber was a type-II superlattice (T2SL). We showed that for a long-wavelength infrared InAs/GaSb T2SL the vertical conductivity hole effective mass can be much smaller than that predicted by the simple band-edge effect mass picture, implying that the vertical hole mobility estimated from the band-edge effective mass can be unduly pessimistic. [ABSTRACT FROM AUTHOR]

We report device performance and provide theoretical analysis of a modified long-wavelength complementary barrier infrared detector structure that incorporates a double tunnel junction contact designed for simpler material growth while retaining the robustness for processing. We also provide analysis of a mid-wavelength quantum dot barrier infrared detector and explain its spectral shape and turn-on characteristics. [ABSTRACT FROM AUTHOR]

The authors report on growth, material characterization, and device performance of infrared photodetectors based on type II InAs/GaSb superlattices using the complementary barrier infrared detector (CBIRD) design. In this paper, control steps for improvement of material quality in terms of surface, structural, and optical properties of infrared detectors grown at Jet Propulsion Laboratory are described. For a specific CBIRD studied, these quality control steps indicate high structural and optical quality of the grown material. Furthermore, single-element detector from the optimized growth conditions exhibit dark current density less than 1 × 10-5 A/cm2 at applied biases up to Vb = 0.36 V (T = 77 K), so this material can be utilized for focal plane arrays development. [ABSTRACT FROM AUTHOR]

In this paper, we present a range of modeling tools that are used in the design and performance evaluation of type-II superlattice detectors. Among these is an optical and photo carrier transport model for the spectral total external QE, which takes into account carrier diffusion length. Using this model, the diffusion length is extracted from external quantum efficiency measurements. It can also be used to fine-tune an optical cavity in relation to the wavelength range of interest for optimal quantum efficiency. Furthermore, an electrical device model for band bending, dark current and doping optimization is described. The modeling tools are discussed and examples of their use are given for MWIR type-II detectors based on InAs/AlSb/GaSb superlattices. [ABSTRACT FROM AUTHOR]

Abstract: We report growth, processing, and characterization of antimonide superlattice long-wavelength infrared photodetectors based on the complementary barrier infrared detector (CBIRD) design. We used photoluminescence measurements for evaluating detector material and studied the influence of the material quality on the intensity of the photoluminescence. We performed direct noise measurements of the superlattice detectors and demonstrated that while intrinsic 1/f noise is absent in superlattice heterodiode, side-wall leakage current can become a source of strong frequency-dependent noise. We developed an effective dry etching process for these complex antimonide-based superlattices that enabled us to fabricate single pixel devices as well as large format focal plane arrays. [Copyright &y& Elsevier]

Abstract: The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from ∼4.2μm to 6μm, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225K. [Copyright &y& Elsevier]

Abstract: The nearly lattice-matched InAs/GaSb/AlSb (antimonide) material system offers tremendous flexibility in realizing high-performance infrared detectors. Antimonide-based superlattice infrared absorbers can be customized to have cutoff wavelengths ranging from the short-wave infrared (SWIR) to the very long-wave infrared (VLWIR). They can be used in constructing sophisticated heterostructures to enable advanced infrared photodetector designs. In particular, they facilitate the construction of unipolar barriers, which can block one carrier type but allow the un-impeded flow of the other. Unipolar barriers are used to implement the barrier infrared detector (BIRD) design for increasing the collection efficiency of photo-generated carriers, and reducing dark current generation without impeding photocurrent flow. We report our recent efforts in achieving state-of-the-art performance in antimonide superlattice based long-wavelength infrared photodetectors using a complementary barrier infrared detector (CBIRD) design. [Copyright &y& Elsevier]