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Optical spectroscopic sensing is a technique that is commonly employed for the identification and compositional analysis of a wide variety of substances, from biological samples to greenhouse gases. High-resolution spectrometers are well established, however, attempts to miniaturise the designs can suffer from adverse effects due to the miniaturisation, for both Fourier transform based interferometric designs, as well as dispersive designs. In this work, a linear array of resonant cavity-enhanced photodiodes is realised with spatially chirped resonance wavelength, offering chip-scale free-space hyperspectral sensing. Resonant cavity-enhanced photodiodes sense over a narrow spectral band, which can be tuned by the thicknesses of the heterostructure. Through this work, multiple narrow spectral bands can be sensed by resonant cavity-enhanced photodiodes on a single chip by grading the thicknesses across the wafer. Photocurrent measurements from a fabricated array determine the wavelength of incident light with an accuracy of ± 2 nm.

Silicon photonics has emerged as the most promising technology for next-generation compact optoelectronic systems, but further development is still required to achieve efficient and reliable on-chip light sources. Direct epitaxial growth of antimonide-based compound semiconductor materials on silicon provides a pathway toward the monolithic integration of new, mid-infrared solid-state light sources and comprehensive photonic circuits on silicon platforms. Such devices have wide-ranging applications in environmental monitoring and medical diagnostics. This paper reports on the realization of a mid-infrared InAsSb light emitting diode directly integrated onto silicon using molecular beam epitaxy. The heteroepitaxial integration of the InAsSb p-i-n device onto silicon was achieved with the use of a novel, antiphase domain-free, GaSb-on-silicon buffer layer. The device exhibited efficient light emission at room temperature, peaking at around 4.5 μm, which corresponds well to the CO2 atmospheric absorption band. An output power of 6 μW and an external quantum efficiency of 0.011% was measured at 300 K. These results demonstrate mid-infrared III-V light emitting diodes can be directly grown on silicon, which is an essential step towards the realization of the next generation, on-chip integrated light sources.

III-Sb barrier detectors suitable for the mid-wave infrared were grown on GaSb by molecular beam epitaxy. Using both bulk-InAsSb and an InAsSb–InAs strained layer superlattice, operation close to room temperature was demonstrated with cutoff wavelengths of 4.82 and 5.79 μm, respectively, with zero-bias operation possible for the bulk-InAsSb detector. X-ray diffraction, temperature dependent dark current, and spectral quantum efficiency were measured, and an analysis based on calculated specific detectivity was carried out. 1/f noise effects are considered. Results indicate that these optimized devices may be suitable as alternatives to InSb, or even HgCdTe, for many applications, especially where available power is limited.

The design, fabrication and characterization of resonant cavity enhanced photodiodes for the short-wave infrared has been investigated. An InGaAsSb absorber and AlGaSb barrier were used in an nBn structure, within a Fabry-Perot cavity bounded by AlAsSb/GaSb DBR mirrors. The resonant cavity design produced a narrow response at ${2.25}~\mu \text{m}$ , with a FWHM of ~26 nm and peak responsivity of 0.9 A/W. The photodiodes exhibited high specific detectivities and low leakage currents at 300 K - $5 \times 10^{10} \,\,\mathrm {cmHz^{1/2}W^{-1}}$ and 0.2 mAcm−2 respectively, with an applied bias voltage of −100 mV. A maximum specific detectivity of $1 \times 10^{11} \,\,\mathrm {cmHz^{1/2}W^{-1}}$ was achieved at 275 K and the detector continued to perform well at high temperatures - at 350 K the peak specific detectivity was $3\times 10^{9} \,\,\mathrm {cmHz^{1/2}W^{-1}}$ . The narrow resonant response of these detectors make them suitable for spectroscopic sensing, demonstrated by measurements of glucose concentrations in water. Concentrations as low as 1 % were discriminated, limited only by the associated electronic systems.

GaSb-based materials can be used to produce high performance photonic devices operating in the technologically important mid-infrared spectral range. Direct epitaxial growth of GaSb on silicon (Si) is an attractive method to reduce manufacturing costs and opens the possibility of new applications, such as lab-on-a-chip MIR photonic integrated circuits and monolithic integration of focal plane arrays (FPAs) with Si readout integrated circuits (ROICs). However, fundamental material dissimilarities, such as the large lattice mismatch, polar-nonpolar character of the III-V/Si interface and differences in thermal expansion coefficients lead to the formation of threading dislocations and antiphase domains, which effect the device performance. This work reports on the molecular beam epitaxial growth of high quality GaSb-based materials and devices onto Si. This was achieved using a novel growth procedure consisting of an efficient AlSb interfacial misfit array, a two-step GaSb growth temperature procedure and a series of dislocation filter superlattices, resulting in a low defect density, anti-phase domain free GaSb buffer layer on Si. A nBn barrier photodetector based on a type-II InAs/InAsSb superlattice was grown on top of the buffer layer. The device exhibited an extended 50 % cut-off wavelength at 5.40 μm at 200 K which moved to 5.9 μm at 300 K. A specific detectivity of 1.5 x1010 Jones was measured, corresponding in an external quantum efficiency of 25.6 % at 200 K.

Resonant cavity-enhanced photodetectors (RCE PDs) present a compelling alternative to broadband detection techniques in the field of gas detection and environmental sensing, due to the distinctive narrow-band absorption fingerprints of gases such as N2O (at 4.5 μm) or CO (4.6 μm). This characteristic aligns well with the operational mode of an RCE PD, whose VCSEL-like architecture results in a tuneable narrow-band spectral response with a significantly enhanced quantum efficiency. Additionally, unlike broadband detectors, RCE PDs are not subject to the broadband BLIP limit due to their high spectral selectivity, while the substantially reduced absorber volume offers commensurately reduced Auger and generation-recombination dark current densities. In this work, we present efforts to extend the operability of these structures beyond 4.0 μm wavelength by employing the type-II InAs/InAsSb superlattice as the absorber material. The tuneable bandgap of this structure allows to achieve and demonstrate a MWIR RCE PD with a highly thermally stable resonant response at ~ 4.45 μm, a Q factor of 85-95, full-width-at-half-maximum of ~ 50 nm and a peak quantum efficiency of 84% at 240 K - features which are promising for detection of gases such as CO and N2O. The broadband BLIP is also achieved at 180 K, a result which could potentially enable thermoelectrically cooled operation in the future. Finally, thanks to the inherent bandgap tunability of the InAs/InAsSb superlattice, extension of resonant response into the LWIR range is achievable with relatively straightforward changes to the already existing RCE PD structure.

Resonant cavity-enhanced photodiodes targeted within the spectral region of absorption by C-H bonds are demonstrated. The 3.0 – 3.3 μm region of the infrared spectrum contains many substances that are useful to measure spectroscopically. However, the measurement of individual substances requires a high spectral specificity, that is achieved by the resonant cavity photodiodes with spectral response widths of

We present III-Sb resonant cavity-enhanced (RCE) photodetectors suitable for gas detection in the mid-wave infrared. AlAsSb/GaSb DBRs and absorbers of bulk InAsSb or a type-II InAsSb-InAs SLS were grown on GaSb, allowing for operation at 3.72 μm or 4.52 μm, with linewidth Δλ 20x reduction in noise compared with a conventional nBn detector with full thickness absorber. At 3.72 μm, performance above the BLIP limit imposed on broadband photodetectors was found by calculating for the specific detectivity.

Inserting an infrared detector architecture into an optical cavity between two high-reflectivity mirrors allows incident light to reflect and pass through the detector multiple times, thereby enhancing absorption within the active region. This allows for a 40-100x thinner optical absorbing region compared to conventional infrared detector structures which reduces the detector dark current and noise and enhances SNR. We report the design, growth, fabrication and characterization of resonant cavity enhanced MWIR photodiodes on GaSb substrates. Devices on GaSb use AlAsSb/GaSb mirrors, AlAsSb spacer layers, and a narrow 96 nm InAsSb absorber. Dark current and detectivity behavior better than equivalent broadband nBn detectors in the literature have been observed. 34nm linewidth detector response is observed. Resonant cavity-enhanced photodiodes with resonant wavelengths of 3.6μm and 3.72μm are demonstrated with dark currents equal to or lower than Rule 07 over the operating temperature range of the device. D∗ in excess of 1×10 10 cm Hz 1/2W -1 at 300K and 8×10 10 cm Hz 1/2W -1 at 250K have been achieved. Amethyst Research has produced packaged resonant-cavity detectors. The 3.6 μm resonant-cavity enhanced photodiode was packaged within an Amethyst Research designed pre-amplifier package with an integrated TEC for detector cooling.

We report the design, growth, processing, and characterization of resonant cavity enhanced photodiodes for the midwave infrared at ∼3.72 μm on GaSb. Using AlAsSb/GaSb mirrors, AlAsSb barrier and spacer layers and a thin 96 nm InAsSb absorber, we observed dark current and detectivity behavior superior to common InAsSb nBn detectors in the literature, with peak specific detectivity values of 8 × 10 10 and 1 × 10 10 cm Hz 1 / 2 W − 1 measured at 250 K and 300 K, respectively. In the same temperature range, the linewidth of the detector response was 60% where the enhancement due to the resonant cavity was ∼20x. We estimate that the devices can operate close to, or slightly above, the background-limited infrared performance limit imposed on broadband detectors for a 300 K scene.

Mid-infrared (MIR) silicon photonics holds the potential for realizing next generation ultracompact spectroscopic systems for applications in gas sensing, defense, and medical diagnostics. The direct epitaxial growth of antimonide-based compound semiconductors on silicon provides a promising approach for extending the wavelength of silicon photonics to the longer infrared range. This paper reports on the fabrication of a high performance MIR photodetector directly grown onto silicon by molecular beam epitaxy. The device exhibited an extended cutoff wavelength at ∼5.5 μm and a dark current density of 1.4 × 10–2 A/cm2 under 100 mV reverse bias at 200 K. A responsivity of 0.88 A/W and a specific detectivity in the order of 1.5 × 1010 Jones was measured at 200 K under 100 mV reverse bias operation. These results were achieved through the development of an innovative structure which incorporates a type-II InAs/InAsSb superlattice-based barrier nBn photodetector grown on a GaSb-on-silicon buffer layer. The difficulties in growing GaSb directly on silicon were overcome using a novel growth procedure consisting of an efficient AlSb interfacial misfit array, a two-step growth temperature procedure and dislocation filters resulting in a low defect density, antiphase domain free GaSb epitaxial layer on silicon. This work demonstrates that complex superlattice-based MIR photodetectors can be directly integrated onto a Si platform, which provides a pathway toward the realization of new, high performance, large area focal plane arrays and mid-infrared integrated photonic circuits.

Direct integration of III–V semiconductor light sources on silicon is an essential step toward the development of portable, on-chip infrared sensor systems. Driven by the presence of characteristic molecular fingerprints in the mid-infrared (MIR) spectral region, such systems may have a wide range of applications in infrared imaging, gas sensing, and medical diagnostics. This paper reports on the integration of an InAs virtual substrate and high crystalline quality InAs/InAsSb multi-quantum wells on Si using a three-stage InAs/GaSb/Si buffer layer. It is shown that the InAs/GaSb interface demonstrates a strong dislocation filtering effect. A series of strained AlSb/InAs dislocation filter superlattices was also used, resulting in a low surface dislocation density of approximately 4 × 107 cm−2. The InAs/InAsSb wells exhibited a strong photoluminescence signal at elevated temperatures. Analysis of these results indicates that radiative recombination is the dominant recombination mechanism, making this structure promising for fabricating MIR Si-based sensor systems.

The design, fabrication, and characterization of a resonant cavity-enhanced photodetector (RCE PD) operating in the long-wavelength infrared regime are demonstrated. The incorporation of the low bandgap InAs/ InAs 0.70 Sb 0.30 type-II strained-layer superlattice into the absorber layer of the detector cavity, along with the high-reflectivity (Rm > 0.9) AlAs 0.08 Sb 0.92/GaSb distributed Bragg reflector pairs, results in resonant enhancement at 7.7–7.8 μm, which is a spectral region relevant in applications in sensing of chemical warfare agents and in medical biomarker diagnostics. These resonant wavelength peaks also display a high quality factor in the range of 76–86 and a small temperature coefficient of 0.52 nm K−1. An nBn architecture, where an Al 0.71 Ga 0.29 As 0.08 Sb 0.92 layer acts as a barrier for majority electrons while minimizing the valence band offset with the absorber, is also incorporated into the cavity in order to improve the electrical properties of the detector. Spectral response measurements yield a peak external quantum efficiency of 14.6% and a peak responsivity of 0.91 A W−1 at 77 K and −0.8 V; meanwhile, a dark current density of 2.0 × 10−4 A cm−2 at 77 K results in a specific detectivity of 3.7 × 1010 cm Hz 1 / 2 W−1, coming close to the theoretical background-limited D * of an ideal broadband photovoltaic detector with the superlattice composition as that of the RCE PD.

We report on a mid-infrared resonant cavity light emitting diode (RCLED) operating at the wavelength of 4.5 µm with a narrow spectral linewidth at room temperature. Compared to a reference LED without a resonant cavity, our RCLED exhibits (85x) higher peak intensity, (13x) higher integrated output power, (16x) narrower spectral linewidth and (7x) superior temperature stability. The device consists of a one-wavelength thick micro-cavity containing an Al0.12In0.88As/InAs0.85Sb0.15 quantum well active region sandwiched between two high contrast AlAs0.08Sb0.92/GaSb distributed Bragg reflector mirrors, grown lattice–matched on GaSb by molecular beam epitaxy. The high spectral brightness, narrow linewidth and superior temperature stability are attractive features, enabling these devices to be used for detection of N2O at 4.5 µm. We show that with only minor adjustments the gases CO2 (4.2 µm) and CO (4.6 µm) are also readily accessible.

High operating temperature i\ud nfrared \ud photo\ud detectors \ud with multi\ud -color function \ud that are\ud capable of monolithic \ud integration \ud are of increasing importance\ud in developing the next \ud generation \ud of \ud mid\ud -IR\ud imag\ud e sensors. \ud Applications of these sensors \ud include defense, medical diagnosis, environmental and \ud astronomical observations. \ud We \ud have \ud investigated a novel \ud InAsSb\ud -based nBnBn heterostructure that combines a state\ud -of-art \ud InAsSb nBn detector with \ud an\ud InAsSb/GaSb heterojuncti\ud on \ud detector\ud . At room temperature, r\ud educti\ud on\ud in the dark current \ud density of more than an order of magnitude \ud was\ud achieved \ud compared to \ud previously investigated\ud InAsSb/GaSb heterojunction \ud dete\ud ctors\ud . \ud Electrical \ud characterization \ud from \ud cryogenic \ud temperatures to roo\ud m temperature\ud confirmed that the nBnBn \ud device was diffusion limited \ud for temperature\ud s above 150K. O\ud ptical\ud measurements\ud demonstrated that the \ud nBnBn detector\ud was \ud sensitive in\ud both \ud the \ud SWIR and MWIR wavelength range at \ud room \ud temperature\ud . The specific \ud detectivity\ud (D*)\ud of the competed nBnBn \ud devices \ud was calculated to be \ud 8.6\ud ×\ud 10\ud 8 \ud cm\ud ·\ud Hz\ud 1/2\ud W\ud -1 \ud at 300K and \ud approximately 1.0\ud ×\ud 10\ud 10 \ud cm\ud ·\ud Hz\ud 1/2\ud W\ud -1 \ud when cooled down to 200K \ud (with\ud 0.3V reverse bias \ud and 1550nm illumination\ud ). In addition, \ud all\ud photodetector layers were \ud grown monolithically on GaAs active \ud layers u\ud sing the interfacial misfit \ud array \ud growth\ud mode\ud . Our results \ud therefore pave the way \ud for the development of \ud new active pixel \ud designs for monolithically integrated mid\ud -IR imaging arrays.

InAs/InAs1-xSbx type-II strained-layer superlattices (SLS) are a structure with potential infrared detection applications, owing to its tunable bandgap and suppressed Auger recombination. A series of medium-wavelength infrared (MWIR) InAs/InAs0.815Sb0.185 SLS structures, grown as undoped absorption epilayers on GaAs, were fabricated using molecular beam epitaxy in order to study the dependence of the ground state transitions on temperature and superlattice period thickness. Photoluminescence peaks at 4 K were obtained with the use of a helium-cooled micro-PL system and an InSb detector, and temperature-dependent absorption spectra were measured in the range 77 K – 300 K on a Fourier Transform Infrared (FTIR) spectrometer, equipped with a 1370 K blackbody source and a DTGS detector. An nBn device sample with the absorber structure identical to one of the undoped samples was also grown and processed with the goal of measuring temperature-dependent spectral response. A model for superlattice band alignment was also devised, incorporating the Bir-Pikus transformation results for uniaxial and biaxial strain, and the Einstein oscillator model for bandgap temperature dependence. Absorption coefficients of several 1000 cm-1 throughout the entire MWIR range are found for all samples, and temperature dependence of the bandgaps is extracted and compared to the model. This and photoluminescence data also demonstrate bandgap shifts consistent with the different superlattice periods of the three samples.

III-V semiconductor heterostructures grown on GaSb and InAs substrates are widely used to produce high performance optoelectronic devices operating in the technologically important mid-infrared spectral range. However, these substrates are expensive, only available in small sizes and have low thermal conductivity. Integration of III-Vs onto silicon substrates offers the opportunity to overcome these shortcomings and opens the possibility of new applications in lab-on-chip MIR photonic integrated circuits. However, the unusual III-V/Si interface and large lattice mismatch presents challenges to epitaxial growth. Here, we report on novel techniques employed to grow high quality Sb-based optoelectronic devices on silicon using molecular beam epitaxy.

InAsSb-based nBn photodetectors were fabricated on GaAs, using the interfacial misfit (IMF) array growth mode, and on native GaSb. At −0.1 V operating bias, 200 K dark current densities of 1.4 × 10−5 A cm−2 (on GaAs) and 4.8 × 10−6 A cm−2 (on GaSb) were measured. At the same temperature, specific detectivity (D*) figures of 1.2 × 1010 Jones (on GaAs) and 7.2 × 1010 Jones (on GaSb) were calculated. Arrhenius plots of the dark current densities yielded activation energies of 0.37 eV (on GaAs) and 0.42 eV (on GaSb). These values are close to the 4 K bandgap of the absorption layers (0.32–0.35 eV) indicating diffusion limited dark currents and small valence band offsets. Significantly, these devices could be used for mid-infrared focal plane arrays operating within the temperature range of cost-effective thermoelectric coolers.

Mid-infrared resonant cavity-enhanced photodetectors (RCE PD) present a promising technology for targeted gas detection. We demonstrate an RCE PD incorporating an InAs/InAsSb superlattice as the detecting element, extending the resonant wavelength beyond 4 µm. AlAsSb/GaSb mirrors and a unipolar barrier active region paralleling an nBn structure are also used, and performance is compared to a conventional broadband nBn detector incorporating the same superlattice. The RCE PD exhibited a Q-factor of ∼90 and an extremely stable resonance wavelength. Peak responsivity was 3.0 A W−1 at 240 K, equalling 84% quantum efficiency, a 5.5 times increase over the reference nBn at the same wavelength. Dark current density was 3.3×10−2 A cm−2 at 240 K, falling to 2.7×10−4 A cm−2 at 180 K. The broadband BLIP limit is approached at 180 K with specific detectivity of 2.1×1011 cm Hz1/2 W−1, which presents the potential of achieving BLIP-limited operation in the thermoelectric cooling regime.

In this work, we demonstrated a mid-infrared resonant cavity light emitting diode (RCLED) operating near 4.2 μm at room temperature, grown lattice-matched on a GaSb substrate by molecular beam epitaxy, suitable for CO2 gas detection. The device consists of a 1λ-thick microcavity containing an InAs0.90Sb0.1 active region sandwiched between two high contrast, lattice–matched AlAs0.08Sb0.92/GaSb distributed Bragg reflector (DBR) mirrors. The electroluminescence emission spectra of the RCLED were recorded over the temperature range from 20 to 300 K and compared with a reference LED without DBR mirrors. The RCLED exhibits a strong emission enhancement due to resonant cavity effects. At room temperature, the peak emission and the integrated peak emission were found to be increased by a factor of ∼70 and ∼11, respectively, while the total integrated emission enhancement was ∼×33. This is the highest resonant cavity enhancement ever reported for a mid-infrared LED operating at this wavelength. Furthermore, the RCLED also exhibits a superior temperature stability of ∼0.35 nm/K and a significantly narrower (10×) spectral linewidth. High spectral brightness and temperature stable emission entirely within the fundamental absorption band are attractive characteristics for the development of next generation CO2 gas sensor instrumentation.

Extended short-wave infrared (SWIR) avalanche photodiodes based on III–V quaternary alloys were grown on GaSb. An InGaAsSb absorber allowed for cut-off wavelengths of 2.2 μm and 2.75 μm, at 77 K and 300 K, respectively. A multiplication layer of AlGaAsSb with Al = 0.9 mole fraction was used, a material recently characterized by our group, allowing for a breakdown voltage of less than 15 V. Linear and 2D arrays were fabricated using BCl3 dry and HF wet-chemical etching, and dielectric passivation layers were tested. These results indicate that extended SWIR single photon detectors can be developed.

Interfacial misfit (IMF) arrays were used to create two APD structures, allowing GaSb absorption layers to be combined with wide-gap multiplication regions, grown using GaAs and Al0.8Ga0.2As, respectively. The GaAs APD represents a proof-of-principle, which is developed in the Al0.8Ga0.2As APD to achieve reduced dark currents, of 5.07 μA cm−2 at 90% of the breakdown voltage, and values for effective k = β/α below 0.2. A random-path-length (RPL) simulation was used to model the excess noise in both structures, taking into account the effects of dead space. It is envisaged that the GaSb absorption regions could be replaced with other materials from the 6.1 A family, allowing for long-wavelength APDs with reduced dark currents and excess noise.

GaSb p–i–n photodiodes were grown on GaAs and Si, using interfacial misfit arrays, and on native GaSb. For the samples grown on GaAs and Si, high-resolution transmission electron microscopy images revealed interface atomic periodicities in agreement with atomistic modeling. Surface defect densities of ~View the MathML source were measured for both samples. Atomic force microscopy scans revealed surface roughnesses of around 1.6 nm, compared with 0.5 nm for the sample grown on native GaSb. Dark current and spectral response measurements were used to study the electrical and optoelectronic properties of all three samples.

We report the impact ionisation coefficients of the quaternary alloy Al0.9Ga0.1As0.08Sb0.92 lattice matched to GaSb substrates within the field range of 150 to 550 kV cm−1 using p-i-n and n-i-p diodes of various intrinsic thicknesses. The coefficients were found with an evolutionary fitting algorithm using a non-local recurrence based multiplication model and a variable electric field profile. These coefficients indicate that an avalanche photodiode not only can be designed to be a function in the mid-wave infrared but also can be operated at lower voltages. This is due to the high magnitude of the impact ionisation coefficients at relatively low fields compared to other III–V materials typically used in avalanche multiplication regions.

Axially doped p-i-n InAs0.93Sb0.07 nanowire arrays have been grown on Si substrates and fabricated into photodetectors for shortwave infrared detection. The devices exhibit a leakage current density around 2 mA/cm(2) and a 20% cutoff of 2.3 μm at 300 K. This record low leakage current density for InAsSb based devices demonstrates the suitability of nanowires for the integration of III-V semiconductors with silicon technology.

An InAsSb nBn detector structure was grown on both GaAs and native GaSb substrates. Temperature dependent dark current, spectral response, specific detectivity (D*) and noise spectral density measurements were then carried out. Shot-noise-limited D*figures of 1.2 10 Jones × 10 and 3.0 10 Jones × 10 were calculated (based upon the sum of dark current and background photocurrent) for the sample grown on GaAs and the sample grown on GaSb, respectively, at 200 K. Noise spectral density measurements revealed knee frequencies of between 124–337 Hz and ∼8 Hz, respectively. Significantly, these devices could support focal plane arrays capable of operating under thermoelectric cooling.

The extended-shortwave infrared wavelength range, encompassing wavelengths from 2.2 to 3 μm, is significantly underdeveloped when compared to the shortwave and midwave infrared bands. Achieving high performance detectors in the extended-shortwave range is desirable; however, it is unclear whether to approach the wavelength range via the detector structures and materials common to the shortwave regime or those common to the midwave regime. Both approaches are studied here. Electrical and optical characteristics of conventional photodiodes and nBn architecture detectors with 2.8 μm cutoff wavelengths are analyzed for detectors with both lattice-mismatched InGaAs and lattice-matched InGaAsSb absorbing regions. Regardless of the absorber material, the nBn detectors show nearly 3 orders of magnitude improvements in performance over the conventional photodiode architecture, and the lattice-matched InGaAsSb nBn exhibits a further reduction in the dark current by more than an order of magnitude when compared to t...

Laser-based stand-off sensing of threat agents (e.g. explosives, toxic industrial chemicals or chemical warfare agents), by detection of distinct infrared spectral absorption signature of these materials, has made significant advances recently. This is due in part to the availability of infrared and terahertz laser sources with significantly improved power and tunability. However, there is a pressing need for a versatile, high performance infrared sensor that can complement and enhance the recent advances achieved in laser technology. This work presents new, high performance infrared detectors based on III-V barrier diodes. Unipolar barrier diodes, such as the nBn, have been very successful in the MWIR using InAs(Sb)-based materials, and in the MWIR and LWIR using type-II InAsSb/InAs superlattice-based materials. This work addresses the extension of the barrier diode architecture into the SWIR region, using GaSb-based and InAs-based materials. The program has resulted in detectors with unmatched performance in the 2-3 μm spectral range. Temperature dependent characterization has shown dark currents to be diffusion limited and equal to, or within a factor of 5, of the Rule 07 expression for Auger-limited HgCdTe detectors. Furthermore, D* values are superior to those of existing detectors in the 2-3 μm band. Of particular significance to spectroscopic sensing systems is the ability to have near-background limited performance at operation temperatures compatible with robust and reliable solid state thermoelectric coolers.

Short-wave infrared barriode detectors were grown by molecular beam epitaxy. An absorption layer composition of In0.28Ga0.72As0.25Sb0.75 allowed for lattice matching to GaSb and cut-off wavelengths of 2.9 μm at 250 K and 3.0 μm at room temperature. Arrhenius plots of the dark current density showed diffusion limited dark currents approaching those expected for optimized HgCdTe-based detectors. Specific detectivity figures of around 7×1010 Jones and 1×1010 Jones were calculated, for 240 K and room temperature, respectively. Significantly, these devices could support focal plane arrays working at higher operating temperatures.

InAs0.79Sb0.21-based nBn photodetectors were fabricated on a GaAs substrate, using the interfacial misfit array growth mode. Reductions in the dark current density of more than two orders of magnitude at 300 K and more than six orders of magnitude at 200 K were found, in comparison with an InAs0.87Sb0.13 p-i-n diode. At −0.5 V applied bias, the dark currents were found to be diffusion limited above 150 K. Background limited infrared photodetection and R0A values in excess of 106 Ωcm2 were observed at 150 K. Spectral response measurements revealed a cut-off wavelength of 5.3 μm at 200 K.