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Cuticle pigmentation has been clearly demonstrated to impact body temperature for several relatively large species of insects, but it was questioned for small insects. Here we used a thermal camera to assess the impact of drosophilid cuticle pigmentation on body temperature when individuals are exposed to light. We compared mutants of large effects within species (Drosophila melanogaster ebonyandyellowmutants). Then we analyzed the impact of naturally occurring pigmentation variation within species complexes (Drosophila americana/Drosophila novamexicanaandDrosophila yakuba/Drosophila santomea). Finally we analyzed lines ofD. melanogasterwith moderate differences in pigmentation. We found significant differences in temperatures for each of the four pairs we analyzed. The temperature differences appeared to be proportional to the differently pigmented area: betweenDrosophila melanogaster ebonyandyellowmutants or betweenDrosophila americanaandDrosophila novamexicana, for which the whole body is differently pigmented, the difference in temperatures was around 0.6°C ±0.2°C. By contrast, betweenD. yakubaandD. santomeaor betweenDrosophila melanogaster DarkandPalelines, for which only the posterior abdomen is differentially pigmented, we detected a temperature difference of about 0.14°C ±0.10°C. This demonstrates that cuticle pigmentation has ecological implications in drosophilids regarding adaptation to environmental temperature.

In this communication, we report on electrical and electro-optical characterizations of InAs/InAsSb Type-II superlattice (T2SL) MWIR photodetector, showing a cut-off wavelength at 5 μm. The device, made of a barrier structure in XBn configuration, was grown by molecular beam epitaxy (MBE) on GaSb substrate. At 150K, dark current measurements shows a device in the Shockley-Read-Hall (SRH) regime but with an absolute value comparable to the state-of-the-art. A quantum efficiency of 50% at the wavelength of 3 μm for a 3 μm thick absorption layer is found in simple pass configuration and front-side illumination. Combined with lifetime measurements performed on dedicated samples through time resolved photoluminescence (TRPL) technique, mobility is extracted from these measurements by using a theoretical calculation of the quantum efficiency thanks to Hovel’s equations. Such an approach helps us to better understand the hole minority carrier transport in Ga-free T2SL MWIR XBn detector and therefore to improve its performance.

In this paper, we study the influence of three different etching depths on electrical and electro-optical properties of nonpassivated T2SL nBn Ga-free pixel detector having a 5μm cut-off wavelength at 150 K. The study shows the strong influence of lateral diffusion length on the shallow etched pixel properties and therefore, the need to perform etching through the absorber layer to avoid lateral diffusion contribution. The lowest dark current density was recorded for a deep-etched detector, on the order of 1 × 10-5 A/cm2 at 150 K and operating bias equal to – 300 mV. The quantum efficiency of this deep-etched detector is measured close to 55 % at 150 K, without anti-reflection coating. A comparison between electro-optical performances obtained on the three etching depths demonstrates that the etching only through the middle of the absorber layer (Mid-etched) allows eliminating lateral diffusion contribution while preserving a good uniformity between the diode’s performance. Such result is suitable for the fabrication of IR focal plane arrays (FPA).

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In this paper, we report on the demonstration of a midwave infrared (MWIR) Ga-free InAs/InAsSb superlattice (SL) barrier detector, grown monolithically on a Si substrate by molecular beam epitaxy (MBE). Prior to the use of MBE, the (1 0 0)-Si substrate was prepared in situ in a metal organic chemical vapor deposition (MOCVD) reactor, where an 800 nm thick GaSb buffer layer was grown. Next, a barrier structure with an active zone made of strain-balanced InAs/InAsSb SL, lattice-matched to GaSb, was epitaxied. Structural characterisations revealed that the material quality was degraded compared with the sample grown on GaSb. The processed Ga-free SL barrier detector has a 100% cut-off wavelength of 5 µm at 150 K, for a bias operation of −500 mV. A combined analysis involving electrical and electro-optical characterisation was performed to identify the operating regimes in this MWIR Ga-free SL barrier structure.

In this paper, a comparison of quantum efficiency and dark current densities of shallow etched and deep etched InAs/GaSb type-II superlattice photodiodes is presented. The detectors were tailored for space applications with measured cut-off wavelengths around 11.2 µm. Bias and temperature dependencies of the QE have been studied showing very low turn on bias (>−25 mV) and very small variation of the peak QE value with temperature. At 70 K, peak quantum efficiencies of shallow and deep etched devices were deduced to 34% and 30%, respectively (without antireflection coating). The difference was attributed to a larger collection area of shallow etched devices, with a collection range of approximately 22 µm outside of the defined pixel area. Diffusion limited dark currents were observed down to 60 K for both shallow and deep etched devices under low reverse bias (∼−200 mV) with dark current densities on the order of 1.7 × 10−5 A/cm2 at 60 K. A gradually increasing influence of generation-recombination (G-R) and trap-assisted tunneling (TAT) was observed at lower temperatures for high reverse bias. The lowest dark current densities were observed for deep etched photodiodes, on the order of 3 × 10−7 A/cm2 at 40 K (Vbias = −100 mV). Detector arrays were fabricated with deep etched 30 µm pitch pixels. Comparably low dark current densities were observed for the detector array pixels under low reverse bias as for the single pixel photodiodes, however a significant increase of the TAT dark current was observed under high reverse bias.

Infrared cameras are used in a wide variety of applications, from military to civilian. Cryogenically cooled IR cameras based on photon-detector arrays are many times more sensitive and faster than uncooled microbolometer thermal imagers.Ga-free InAs/InAsSb type 2 superlattice (T2SL) based devices have been recently fabricated and they showed a first realization of MWIR (Mid-Wave InfraRed) broadband detection up to 5μm. However the band parameters (band offsets, effect of strain, effective mass) of this material system have not been determined accurately, thus limiting the understanding and the prediction of the electronic properties of the devices. In this work we determined the relevant parameters via magnetoabsorption measurements performed on dedicated T2SL samples. Interband magneto-optical transitions lead to an accurate mapping of the Landau levels. The Landau level energies have been calculated using an 8 bands k.p model and the comparison with the experimental data provided a clear description of the T2SL band structure at low temperatures.

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In this work, we investigated the effects of 63 MeV proton irradiation on the electrical performance of long-wave infrared InAs/GaSb type-II superlattice barrier detectors. The dark current density increase due to displacement dose effects does not exceed a factor of 2.6, regardless of the absorber thickness, when measured after a proton fluence of 8×1011 H+/cm2 at 100 K. Subsequent analysis showed that the dark current changes behavior after irradiation, and the dominant current is no longer diffusion but generation–recombination and trap-assisted tunneling. Device simulation also allowed us to extract a minority carrier lifetime before and after irradiation, which decreases with increasing fluence as a result of the 63 MeV proton-induced mild material degradation.

Raising the operating temperature of the midwave infrared (MWIR) cameras up to 150 K without penalizing the performances of the photodetectors is one of the main challenges of the domain. Moreover, extending the range of detection up to 5 μm brings many advantages. Ga-free InAs/InAsSb superlattice based devices have been recently fabricated and they showed the first realization of these objectives. However, the band parameters (band offsets, effect of strain, effective mass) of this system have not been determined accurately, thus limiting the understanding and the prediction of the electronic properties of the devices. In this work, we determined the relevant parameters via magnetoabsorption measurements performed on dedicated superlattices. Interband magneto-optical transitions lead to an accurate mapping of the Landau levels. The Landau level energies have been calculated using an 8-band k ⋅ p model, and the comparison with the experimental data provided a clear description of the type 2 superlattice miniband structure at 4.2 and 150 K, as well as its MWIR absorbance.

International audience; In this paper, the influence of etching depth on the dark current and photo-response of a mid-wave infrared Ga-free T2SL XBn pixel detector is investigated. Two wet chemical etching depths have been considered for the fabrication of a non-passivated individual pixel detector having a cut-off wavelength of 5 µm at 150 K. This study shows the strong influence of the lateral diffusion length of a shallow-etched pixel on the electro-optical properties of the device. The lowest dark current density was recorded for the deep-etched detector, on the order of 1 × 10−5 A/cm2 at 150 K and a bias operation equal to −400 mV. The corresponding quantum efficiency was measured at 60% (without anti-reflection coating) for a 3 µm thick absorbing layer. A comparison of experimental results obtained on the two kinds of etched pixels demonstrates the need for a deep-etching process combined with efficient passivation for FPA manufacturing.

Les materiaux semiconducteurs III-V de la « famille » des antimoniures (III-Sb), c'est-a-dire les semiconducteurs GaSb, InAs, AlSb et leurs alliages, presentent des raccordements de bande interdite si particuliers qu'ils permettent la conception de structures tres originales. C'est le cas des structures a barriere dites XBn qui se sont imposees ces dernieres annees comme l'un des standards des dessins de photodetecteurs infrarouges haute performance refroidis.

In this communication, we report on electrical and electro-optical characterizations of InAs/GaSb Type-II superlattice (T2SL) LWIR photodetector, showing cut-off wavelengths at 11μm at 77K. The devices, made of barrier structures in XBp configuration, were grown by molecular beam epitaxy (MBE) on GaSb substrate. Experimental measurements on samples were made by photoresponse spectra, by capacitance-voltage (C-V) and dark current-voltage (I-V) characteristics performed as a function of temperature.

International audience; Stability over time has recently become a figure of merit of major importance to compare the performances of infrared focal plane arrays (FPA) of different technologies. Indeed, this parameter dictates how often the calibration of operational electro-optical systems has to be done, and thus reflects the availability of the system during an operational mission. The stability over time is generally estimated through fixed pattern noise (FPN) and residual fixed pattern noise (RFPN) measurements after a two-point correction. However, each laboratory or industrial has its own protocols and criteria, such that published results cannot be easily compared. Recent studies also showed that random telegraph signal (RTS) noise, which leads to flickering pixels, can strongly affect the image quality, so the question arises as to wether these RTS pixels have an effect on RFPN. In this paper, we describe our experimental protocol to evaluate the stability over time of an FPA and to count up/classify flickering pixels. We then present the results obtained on a T2SL MWIR Integrated Detector Dewar Cooler Assembly (IDDCA) provided by IRnova. Our measurements show that the stability over time of the T2SL MWIR IDDCA are excellent: first, in terms of FPN/RFPN; then, in terms of RTS noise with only a few blinking pixels. We also show that the RTS pixels having an effect on the RFPN are fully detected by the algorithm used to rule out defective pixels before calculating RFPN.

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International audience; Stability over time has recently become a figure of merit of major importance to compare the performances of infrared focal plane arrays (FPA) of different technologies. Indeed, this parameter dictates how often the calibration of operational electro-optical systems has to be done, and thus reflects the availability of the system during an operational mission. Recent studies also showed that random telegraph signal (RTS) noise, which leads to flickering pixels, can strongly affect the image quality. The stability over time is generally estimated through fixed pattern noise (FPN) and residual fixed pattern noise (RFPN) measurements after a two-point correction. However, each laboratory or industrial has its own protocols and criteria, such that published results cannot be easily compared. In this paper, we describe our experimental protocol to evaluate the stability over time of a FPA and to count up / classify flickering pixels. We then present the results of two measurement campaigns realized on a T2SL MWIR Integrated Detector Dewar Cooler Assembly (IDDCA) provided by IRnova: the first, long term study was dedicated to the measurement of FPN/RFPN (estimated with two different algorithms); with the second study, dedicated to RTS noise, we tried to realize a classification of flickering pixels, based on the jump amplitude and the jump frequency. Our measurements show that the stability over time and correctability of the T2SL MWIR IDDCA are excellent. Highlights :-Stability over time and RTS noise of a commercial T2SL midwave infrared FPA have been investigated.-RFPN/TN ratio stays lower than unity for more than 7 weeks-number of RTS pixels is as low as 10 for a 5-minutes long measurement

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For very high performance infrared (IR) photodetectors, characterization is necessary to understand the impact of fabrication processes. A useful tool to characterize photodetectors is the Electron Beam Induced Current (EBIC) technique. For Very-Long Wavelength InfraRed (VLWIR) HgCdTe (MCT) samples, the dark current is such that measurements can be very noisy. We develop our EBIC setup with the implementation of a cold shield and an AC operation to filter out the parasitic flux and to increase the signal to noise ratio. EBIC measurements are performed on VLWIR HgCdTe and Medium Wavelength InfraRed (MWIR) T2SL photodetectors. For the VLWIR MCT-based sample with a cut-off wavelength of 15 µm at 77 K we determine a diffusion length of 11.4 µm at 120 K while discussing the validity of theoretical models in our situation. This result is compared to a Spotscan measurement. We also determine the minority carrier diffusion length of the MWIR InAs/InAsSb based type-II superlattice (T2SL) with a cut-off wavelength of 4.5 µm at 120 K. These results are discussed in regard to the literature.

International audience; Type-II InAs/GaSb superlattice (T2SL) has recently matured into a commercially available technology addressing both MWIR and LWIR spectral domains. As the prerequisites such as Quantum Efficiency (QE) and dark current were met, more advanced figures of merits related to the ElectroOptic (EO) system as a whole can now be studied to position this technology. In this paper, we focus on modulation transfer function (MTF) measurements. Knowing the MTF of a detector is indeed of primary importance for the EO system designers, since spatial filtering affects the system range. We realized MTF measurements on a 320 × 256 MWIR T2SL FPA provided by IRnova, using a Continuously Self Imaging Grating (CSIG). The advantage of this experimental configuration is that no high performance projection optics is required thanks to the self-imaging property (known as Talbot effect) to project a pattern with known spatial frequencies on the photodetector. Besides, the pattern being propagation invariant, alignment is easier and the bench does not require exact knowledge of the focal plane distance to operate, opening measurement in Integrated Detector Dewar Cooler Assembly (IDDCA) configuration. Extracted from measurements, the pixel size is 26 µm for a pitch of 30 µm.

In this paper, results from the development of LWIR and VLWIR InAs/GaSb type-II infrared photodetector arrays are presented. Dark currents comparable to the HgCdTe benchmark (Rule07) have been observed and the quantum efficiencies of the detectors exceed 30 %. Bias and temperature dependencies of the QE have been studied showing very low turn on bias (~-25mV) and no variation of the peak QE value with temperature. These results show that there are no unintentional barriers in the detector structures and that the diffusion lengths are long enough to provide efficient collection of carriers. Initial results from the extension of the cut-off wavelength from 11 μm to 14 μm are also presented as well as initial results from photodiodes with thicker absorbers to enhance the QE.

International audience; Type-II InAs/GaSb superlattice (T2SL) has recently matured into a commercially available technology addressing both MWIR and LWIR spectral domains. As the prerequisites such as Quantum Efficiency (QE) and dark current were met, more advanced figures of merits related to the ElectroOptic (EO) system as a whole can now be studied in order to position this technology. In this paper, we focus on modulation transfer function (MTF) measurements. Knowing the MTF of a detector is indeed of primary importance for the EO system designers, since spatial filtering affects the system range. We realized MTF measurements on a 320x256 MWIR T2SL FPA provided by IRnova, using a Continuously Self Imaging Grating (CSIG). The advantage of this experimental configuration is that no high performance projection optics is required. Indeed, the CSIG exploits the self-imaging property (known as Talbot effect) to project a pattern with known spatial frequencies on the photodetector. Such MTF measurements have never been done in Integrated Detector Dewar Cooler Assembly (IDDCA) configuration, so we had to study the effect of the vibrations induced by the cryocooler. Vibrations indeed affect the MTF measurement in the same way electrical diffusion would do. Using three accelerometers we optimized our experimental setup and extracted MTF measurements with reduced vibrations. The pixel size is 26μm for a pitch of 30 μm.

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International audience; In operational electro-optical systems, infrared focal plane arrays (IR FPA) are integrated in cryocoolers which induce vibrations that may strongly affect their modulation transfer function (MTF). In this paper, we present the MTF measurement of an IR FPA sealed in its cryocooler. The method we use to measure the MTF decorrelates operational constraints and the technological limitations of the IR FPA. The bench is based on the diffraction properties of a continuously self imaging grating (CSIG). The 26 µm pixel size extracted from the MTF measurement is in good agreement with the expected value.

International audience; In this work, we report on the determination of band discontinuities and energy band diagram of the Ga0.6Al0.4As0.034Sb0.966(p)/Ga0.6Al0.4As0.034Sb0.966(n)/InAs0.9Sb0.1 double interface at equilibrium and room temperature, by capacitance-voltage measurements (C-V). Mesa diodes, with three different diameters are characterized and physical quantities like doping concentration in the unintentionally doped (n.i.d) InAsSb material and diffusion potentials at interfaces are extracted from C-V data. Finally, the energy band diagram of the structure is drawn and experimental values of energy band offsets are deduced and compared to those obtained by a numerical simulation.

International audience; The knowledge of carrier concentration of doped or non-intentionally doped layer structures grown by Molecular Beam Epitaxy (MBE) is crucial to fabricate and manage design of new advanced photodetectors called "barrier structures". This communication reports on capacitance-voltage (C-V) study on MOS structure. Simulation to define specific MOS design, allowing doping layer concentration extraction by measurements, is performed. MOS structures based on InAs/GaSb Longwave infrared (LWIR) superlattice have been fabricated and characterized. Results obtained were analyzed and compared with simulations.

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Design of InAs/GaSb type-II superlattice (T2SL) infrared barrier detectors is theoretically investigated. Each part of the barrier structures is studied in order to achieve optimal device operation at 150 K and 77 K, in the midwave and longwave infrared domain, respectively. Whatever the spectral domain, nBp structure with a p-type absorbing zone and an n-type contact layer is found to be the most favourable detector architecture allowing a reduction of the dark-current associated with generation-recombination processes. The nBp structures are then compared to pin photodiodes. The MWIR nBp detector with 5 μm cut-off wavelength can operate up to 120 K, resulting in an improvement of 20 K on the operating temperature compared to the pin device. The dark-current density of the LWIR nBp device at 77 K is expected to be as low as 3.5 × 10−4 A/cm2 at 50 mV reverse bias, more than one decade lower than the usual T2SL photodiode. This result, for a device having cut-off wavelength at 12 μm, is at the state of the art compared to the well-known MCT ‘rule 07’.

We studied the Ga-free InAs/InAsSb type-II superlattice (T2SL) period, thickness and antimony composition, in order to define an optimized structure suitable for detection of the full mid-wavelength infrared domain (MWIR). The SL structures were fabricated by MBE on n-type GaSb substrates and exhibited cut-off wavelengths between 5μm and 5.5μm at 150K. The growth procedure used to achieve strain-balanced structures is reported and first structural and optical results, made of high-resolution Xray diffraction pattern, AFM image scan, photoluminescence (PL) and time resolved photoluminescence measurements (TRPL), are presented and analyzed.

This paper reports studies on spatial characteristics of Mid Wave InfraRed (MWIR) InAs/GaSb superlattices (T2SL) photodetectors. Modulation Transfer Function (MTF) measurements on commercial T2SL MWIR Focal Plane Array (FPA) are reported, using a Continuously Self Imaging Grating (CSIG). We find that measurements of the pixel size can be reliably achieved thanks to a new approach of data processing. Next, a new class of radiometric characterization, called "correctability", or ability for FPA pixels to durably keep the same behavior when exposed to a given radiometric flux, has been investigated on. Gain and offset corrections and Residual Fixed Pattern Noise (RFPN) measurements have also been made. The results obtained confirm the potentiality of high performance T2SL infrared photodetectors.

International audience; In this paper, structural, optical and electrical characterizations of longwave infrared barrier detectors based on the InAs/GaSb superlattice are reported and analyzed. The fabricated detectors exhibited a 50% cut-off wavelength around 10.5μm at 80K measured by photoluminescence and spectral response. The dark current density was 8.4×10-4A/cm2at 80K and a performance analysis combining spectral response, dark current-voltage characteristic and capacitance-voltage measurement curves was performed to determine the operating bias and the dark current regimes at different biases. Dark current simulations were also performed to better understand limiting dark current mechanisms of the device performance.

InAs/GaSb superlattice pin photodiodes, having an asymmetric period design, exhibited cut-off wavelength in the midwave infrared domain (MWIR) at 5 μm at 77 K. Electrical characterizations including dark-current and capacitance–voltage measurements were performed on single detectors in the temperature range (77–300 K). The SL photodiode measurements revealed carrier concentrations of about 6 × 1014 cm−3 at 77 K, dark-current densities J = 4 × 10−8 A/cm2 at 77 K for Vbias = −50 mV and the measured R0A product is higher than 1.5 × 106 Ω cm2 at 77 K. Comparison to classical pin diodes with symmetric period design show that the differential resistance area product is improved by more than one order of magnitude. This result obtained demonstrates the strong influence of the period on the electrical properties of SL MWIR photodiodes.

In this communication, we report results obtained on a new InSb/InAlSb/InSb ‘bariode’, grown by MBE on (100)- oriented InSb substrate. Because of a very weak valence band offset with InSb (~ 25meV), InAlSb is a good candidate as a barrier layer for electrons. However, due to lattice mismatch with the InSb substrate, careful growth study of InAlSb was made to insure high crystal quality. As a result, InSb-based nBn detector device exhibits dark current density equals to 1x10 -9 A.cm -2 at 77K: two decades lower than Insb standard pin photodiode with similar cut-off wavelength. Moreover, compared to standard pn (or pin) InSb-based photodetectors fabricated by implanted planar process or by molecular beam epitaxy (MBE), we demonstrate that the reachable working temperature, around 120 K, of the InSbbased nBn detector is respectively higher than 40 K and 20 K than the previous. Such result demonstrates the potentiality of Insb detectors with nBn architecture to reach the high operating temperature.

GaSb-rich superlattice (SL) p-i-n photodiodes grown by molecular beam epitaxy were studied theoretically and experimentally in order to understand the poor dark current characteristics typically obtained. This behavior, independent of the SL-grown material quality, is usually attributed to the presence of defects due to Ga-related bonds, limiting the SL carrier lifetime. By analyzing the photoresponse spectra of reverse-biased photodiodes at 80 K, we have highlighted the presence of an electric field, breaking the minibands into localized Wannier-Stark states. Besides the influence of defects in such GaSb-rich SL structures, this electric field induces a strong tunneling current at low bias which can be the main limiting mechanism explaining the high dark current density of the GaSb-rich SL diode.

International audience; In this communication we report on temperature dependence performances of short period InAs/GaSb pin superlattice (SL) photodiode grown by Molecular Beam Epitaxy on p-type GaSb substrate. SL symmetrical structure with 3 mu m thick active region, adapted for detection in the MWIR domain with cutoff wavelength varying from 4.6 mu m to 5.5 mu m in the temperature range 80-300 K, was processed in mesa photodiode in order to perform dark current measurements as a function of temperature. Extracted from current-voltage characteristics. R(0)A products above 1 x 10(6) Omega cm(2) at 80K and around 0.15 Omega cm(2) at 200 K were measured, and the quantitative analysis of the J-V curves allowed us to identify the dominant dark current mechanism in each operating temperature range. As a result, SL photodiode is dominated by generation-recombination (GR) processes at low temperature and becomes diffusion limited above 140 K. Such results are discussed and minority carrier lifetimes were extracted from J-V curve fitting.

International audience; In this paper, we present resistivity and Hall measurements on InAs/GaSb Superlattice (SL) grown by Molecular Beam Epitaxy (MBE) on GaAs semi-insulating substrate. Measurements have been carried out under hydrostatic pressure up to 1300 MPa in the temperature range 80-300 K. We observe that the sample exhibits a reproducible change in conductivity type. The SL is n-type at high temperatures range whereas it is p-type at low temperature. The characteristic temperature T-ch at which the switch of conductivity type occurs increases with pressure from T-ch = 190 K to 280 K at highest pressure. The room temperature results are characterized by a strong increase of resistivity with pressure. The room-temperature Hall mobility varies from 1350 cm(2)/V s for ambient pressure to 345 cm(2)/V s for P = 1210 MPa. This strong effect of pressure on electrical transport properties of material suggests that at room temperature at least two types of electrons respectively with high and low mobility take part in the conduction process. The low mobility carriers could be related to the L mini band. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

We report on optical gain calculations of a dilute-nitride mid-infrared laser structure designed to be grown on InAs substrate. The active region is composed of several strain-compensated type-II “W”-like InAsN/GaSb/InAsN quantum wells adapted to operate near 3.3 μm at room temperature. For typical injected carrier density σ = 1.1012 cm − 2 , the theoretical laser structure performances reveal a gain value at around 1000 cm − 1 at 300 K, inducing a modal gain value equal to 50 cm − 1 . Low radiative current densities lower than 100 A/cm 2 are predicted, indicating that this dilute-nitride structure could operate at 300 K with small threshold current density.

International audience; Dilute-nitride InAsN/GaSb/InAsN "W" laser structure is theoretically investigated and compared with similar nitride-free InAs/GaSb/InAs "W" structure. The two laser diodes, to be grown on (001) InAs substrate, are designed to operate at 3.3μm at room temperature. Their performances are evaluated in terms of modal gain and radiative efficiency characteristics deduced from optical gain calculation. We find that the inclusion of nitrogen in the laser active region improves optical gain performances leading to peak gain values of the order of 1000cm-1 for typical injected carrier concentration of 1.5 x 1018 cm-3. Modal gain value equal to 70 cm-1 can be achieved and radiative current density inferior to 100 A/cm2 is predicted. These results demonstrate that the dilute-nitride InAsN/GaSb/ InAsN laser structure is very attractive for room temperature operation in the midwave infrared domain.

We report on the structural characterization of short period type-II InAs/GaSb superlattices (SLs) adapted for mid-infrared detection. These structures, grown by molecular beam epitaxy (MBE) on n-type GaSb substrates, are made up of 10 InAs monolayers (MLs) and 10 GaSb MLs and a strain balanced condition is obtained by inserting an InSb ML at the interface between InAs and GaSb in each superlattice's period. From cross-sectional transmission electron microscopy (TEM) measurements, the interface structure is analysed in detail. Very homogeneous and smooth InAs and GaSb layers all over a 50 periods SL structure are observed and high-resolution images bring out the InSb ML inserted between InAs and GaSb. Room temperature absorbance spectroscopy measurements have been performed on strain-compensated SLs including 50, 100, 300 and 400 periods, for a total absorption zone thickness of 0.32, 0.64, 1.92 and 2.56 μm, respectively. The spectra display reproducible and well-defined features with an absorption coefficient varying between 2×10 3 and 4×10 3 cm −1 in the 3–5 μm mid-infrared domain, a sign of high-quality samples suitable for detection.