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International audience; Background and Aims; Genetically modified mice have been used extensively to study human disease. However, the data gained are not always translatable to humans because of major species differences. Liver‐humanized mice (LHM) are considered a promising model to study human hepatic and systemic metabolism. Therefore, we aimed to further explore their lipoprotein metabolism and to characterize key hepatic species‐related, physiological differences.Approach and Results: Fah−/−, Rag2−/−, and Il2rg−/− knockout mice on the nonobese diabetic (FRGN) background were repopulated with primary human hepatocytes from different donors. Cholesterol lipoprotein profiles of LHM showed a human‐like pattern, characterized by a high ratio of low‐density lipoprotein to high‐density lipoprotein, and dependency on the human donor. This pattern was determined by a higher level of apolipoprotein B100 in circulation, as a result of lower hepatic mRNA editing and low‐density lipoprotein receptor expression, and higher levels of circulating proprotein convertase subtilisin/kexin type 9. As a consequence, LHM lipoproteins bind to human aortic proteoglycans in a pattern similar to human lipoproteins. Unexpectedly, cholesteryl ester transfer protein was not required to determine the human‐like cholesterol lipoprotein profile. Moreover, LHM treated with GW3965 mimicked the negative lipid outcomes of the first human trial of liver X receptor stimulation (i.e., a dramatic increase of cholesterol and triglycerides in circulation). Innovatively, LHM allowed the characterization of these effects at a molecular level.Conclusions: LHM represent an interesting translatable model of human hepatic and lipoprotein metabolism. Because several metabolic parameters displayed donor dependency, LHM may also be used in studies for personalized medicine.

The hypothalamus is key in the control of energy balance. However, strategies targeting hypothalamic neurons have failed to provide viable options to treat most metabolic diseases. Conversely, the role of astrocytes in systemic metabolic control has remained largely unexplored. Here, we show that obesity promotes anatomically restricted remodeling of hypothalamic astrocyte activity. In the paraventricular nucleus (PVN) of the hypothalamus, chemogenetic manipulation of astrocytes results in bidirectional control of neighboring neuron activity, autonomic outflow, glucose metabolism, and energy balance. This process recruits a mechanism involving the astrocytic control of ambient glutamate levels, which becomes defective in obesity. Positive or negative chemogenetic manipulation of PVN astrocyte Casup2+/supsignals, respectively, worsens or improves metabolic status of diet-induced obese mice. Collectively, these findings highlight a yet unappreciated role for astrocytes in the direct control of systemic metabolism and suggest potential targets for anti-obesity strategy.

SummaryThe hypothalamus is key in the control of energy balance. However, to this day strategies targeting hypothalamic neurons failed to provide viable option to treat most metabolic diseases. Conversely, the role of astrocytes in systemic metabolic control has remained largely unexplored. Here we show that obesity promotes anatomically restricted remodeling of hypothalamic astrocyte activity. In the paraventricular nucleus (PVN) of the hypothalamus, chemogenetic manipulation of astrocytes results in bidirectional control of neighboring neuron activity, autonomic outflow, glucose metabolism and energy balance. Such process recruits a mechanism involving the astrocytic control of ambient glutamate levels, which becomes defective in obesity. Positive or negative chemogenetic manipulation of PVN astrocyte Ca2+ signals respectively worsen or improves metabolic status of diet-induced obese mice. Collectively, these findings highlight a yet unappreciated role for astrocyte in the direct control of systemic metabolism and suggest potential targets for anti-obesity strategy.

IntroductionAlthough the physiological role of the C-terminal hydrolase domain of the soluble epoxide hydrolase (sEH-H) is well investigated, the function of its N-terminal phosphatase activity (sEH-P) remains unknown.ObjectivesThis study aimed to assess in vivo the physiological role of sEH-P.MethodsCRISPR/Cas9 was used to generate a novel knock-in (KI) rat line lacking the sEH-P activity.ResultsThe sEH-P KI rats has a decreased metabolism of lysophosphatidic acids to monoacyglycerols. KI rats grew almost normally but with less weight and fat mass gain while insulin sensitivity was increased compared to wild-type rats. This lean phenotype was more marked in males than in female KI rats and mainly due to decreased food consumption and enhanced energy expenditure. In fact, sEH-P KI rats had an increased lipolysis allowing to supply fatty acids as fuel to potentiate brown adipose thermogenesis under resting condition and upon cold exposure. The potentiation of thermogenesis was abolished when blocking PPARγ, a nuclear receptor activated by intracellular lysophosphatidic acids, but also when inhibiting simultaneously sEH-H, showing a functional interaction between the two domains. Furthermore, sEH-P KI rats fed a high-fat diet did not gain as much weight as the wild-type rats, did not have increased fat mass and did not develop insulin resistance or hepatic steatosis. In addition, sEH-P KI rats exhibited enhanced basal cardiac mitochondrial activity associated with an enhanced left ventricular contractility and were protected against cardiac ischemia-reperfusion injury.ConclusionOur study reveals that sEH-P is a key player in energy and fat metabolism and contributes together with sEH-H to the regulation of cardiometabolic homeostasis. The development of pharmacological inhibitors of sEH-P appears of crucial importance to evaluate the interest of this promising therapeutic strategy in the management of obesity and cardiac ischemic complications.

Introduction: Conventional mouse models do not fully recapitulate human cardiometabolic diseases (CMD), e.g. , atherosclerosis and nonalcoholic steatohepatitis (NASH), due to species differences in metabolism. Liver-humanized mice (LHM), i.e. , mice repopulated with human hepatocytes, have been shown to be an improved translatable model to study human hepatic and lipoprotein metabolism. Hypothesis: As dietary challenge is often used to induce CMD in animal models, we sought to characterize lipoprotein and lipid metabolism in LHM challenged by different diets. Methods: Immune-deficient FRGN mice receiving hepatocytes from different human donors (LHM) or NOD mouse (liver-murinized mice, LMM) were fed a high-fat/high-sucrose diet (HFHSD) for 8 weeks or a high-fat/high-fructose/high-cholesterol diet (NASH-diet) for 8, 12, 16 or 20 weeks. Plasma lipids and lipoproteins were quantified after size-exclusion chromatography separation or by routine clinical assays. Cholesterol in the descending aorta was analyzed by GC-MS. Histologic analysis of hearts or livers was done using hematoxylin/eosin or Oil Red O staining, and anti-mouse CD68-antibody was used to detect murine macrophages. Results: Compared with LMM, LHM fed either HFHSD or NASH-diet accumulated plasma cholesterol and triglycerides within LDL and triglyceride-rich particles (VLDL and remnants). However, only the NASH-diet induced a notable hyperlipidemia and a substantial increase in cholesteryl esters within the aorta. NASH-diet also determined a clear accumulation of neutral lipids and CD68-positive cells in the aortic valves of LHM. Similarly, hepatocyte ballooning, liver steatosis and fibrosis were also induced by the NASH-diet. All these pathologic changes occurred during diet challenge at different time points. Conclusions: LHM developed severe hyperlipidemia, atherosclerosis and NASH when fed a NASH-diet, but not on HFHSD. The high quantity of cholesterol in the NASH-diet likely compensates for the high utilization of cholesterol of LHM due to their known increase in bile acid synthesis, prompting dyslipidemia and CMD. LHM fed a NASH-diet is an improved model for human CMD and for the development of therapeutic strategies rapidly translatable to the human condition.

Be + implantation technology has been applied to realize p + /n − junctions in quaternary GaInAsSb n − alloys grown on GaSb substrates by liquid phase epitaxy. 2 μm cut-off mesa homojunctions have been prepared and characterized: the external quantum efficiency measured without any antireflecting coating reaches η ext = 0.5 at 1.8 μm. Room temperature dark reverse current densities J rev (300K) = 1–5 mA cm −2 measured at V = −0.5 V are 10–100 times lower than those usually measured in GalnAsSb photodetectors; at low reverse polarization voltage the rapid decrease in the current levels as a function of the temperature leads to a strong increase in the performances of the photodiodes using simple Peltier cooling (J rev (220 K) = 12 μA cm −2 at V = − 0.2 V). In the forward direction the behaviour of the dark currents as a function of the temperature leads us to conclude that diffusion is the dominant mechanism in these photodiodes in the range 320−220 K.

Liquid phase epitaxial growth of Te‐compensated GaSb results in a very low doped n− GaSb epilayer (n≊1015 cm−3). Be+‐implanted photodiodes produced from this material exhibit voltage breakdown values reaching 70 V. Generation‐recombination lifetimes in the space charge region around 10−8 s have been deduced from these diode photoelectrical properties. The high value of the space charge width leads to an efficient redshift due to the electroabsorption. The variation of the absorption coefficient value is 1350 cm−1 at 1.72 μm for a variation of the electric field maximum of 1.2×105 V/cm.

The effects of chemical sulphuration on GaSb mesa photodiodes performance were investigated by electrical characterization. (NH 4 ) 2 S treatment was found to be very effective in reducing the reverse dark currents by one module value, leading them down to I = 0.2 μ A (V = 1 V) for a φ = 60μ m diameter diode. The capacitance variation versus frequency, investigated from 10 kHz to 1 MHz, becomes flat over the whole range of frequency, attesting of a volume conduction mechanism. These performances exhibited a remarkable stability during 1 year, without encapsulation. The X-ray photoelectron spectrum of the Sb 3d level shows that after (NH 4 ) 2 S treatment the surface is free of native Sb oxides, Sb-.sbnd;S bonds being created by the adsorption of sulphur atoms on the surface These surface modifications are responsible for the observed improvement in characteristics and their stability.

Some features of the band structure of GaSb have led to a renewed interest in this material. It is well known that Ga(Al)Sb alloys are good candidates to realize avalanche photodetectors, due to their high hole kp/electron kn ionization coefficient ratio. In addition, recent studies have shown GaSb to be attractive for realizing tunneling barriers exhibiting a high value of the peak-to-valley current ratio or IR photodectectors. In order to optimize such devices, the passivation of GaSb is of great interest. Unfortunately, very few investigations have been reported in the literature on GaSb passivation. This paper reports experimental results concerning GaSb surface passivation using a chemical sulfuration method. Physicochemical analysis is attempted through ellipsometric, photoluminescence, and Auger electron spectroscopy measurements. Polluting oxygen and carbon agents are found to be removed from the surface using this process, leading to Schottky diodes of better quality. In addition, the sulfur treatment is shown to stabilize the cleaned surface.

The validity of the determination of the ionization coefficients deduced from the experimental measurement of photocurrent multiplication Mph in GaAlSb diodes, in which the electric‐field profile is nonlinear and successive pure hole and pure electron injections cannot be made, are compared and discussed. Three methods for determining ionization coefficients kp and kn are discussed: (i) adjusting kp and kn in order to fit the experimentally observed Mph values using an approximated linear electric field; (ii) the same method applied to a more realistic electric‐field profile; (iii) the Grant method in which kp and kn are calculated from the results of multiplication measurements in the case of pure injections and using this last electric‐field profile. It is concluded that when the condition of pure injection is not fulfilled the Grant method may lead to erroneous k values and the adjustment method is more valid.

Be + ion implantation into Te-doped Ga(Al)Sb ( x Al ≈ 4% ) epilayers was performed to realize the p + layer of a p + /n − GaAlSb/GaSb n + IR avalanche photodetector. A double implantation using 100+50 keV energies and fluences around 10 13 cm −2 is found to be a convenient procedure to produce a junction depth of 0.5 μm. Damage levels created by Be + ions in GaAlSb layers are simulated and investigated through channelling measurements and it is seen that heat treatments (15 min, 450 °C, H 2 ) improve the activation. This paper clearly shows that Be + ion implantation leads to a low damage level in this III–V compound.

Implantation of Be+ ions into GaAISb epilayers is used to realize thep + layer of the Ga0.96Al0.04Sb p+/Ga0.96Al0.04Sbn − /GaSbn + (1.55 /Μm) avalanche photodetector whose performances are detailed in Ref. (1). The GaAISb layers are grown using liquid phase epitaxy (LPE); the quality of these as-grown layers is shown through photoluminescence and channeling measurements. The last part of this paper is devoted to the damaging level in the Be+-implanted layers. Some annealing techniques are presented as a mean of restoration of the implanted layers. It is clear from the results that the Be+ ion implantation leads to a low damage level in this III-V compound.

An evaluation of the performance of a separated absorption multiplication avalanche photodiode based on Ga 0.7 In 0.3 As 0.27 Sb 0.73 (energy gap E g = 490 meV) for absorption and Ga 0.95 Al 0.05 Sb ( E g = 790 meV) for multiplication is presented. The calculation involves the measured ionization coefficients for holes and electrons in Ga 0.95 Al 0.05 Sb. The various steps of the calculation and the optimization of the minimum detectable power P md are described. A P md value of −41.7 dB m is predicted for a 2 GHz band pass device realized with attainable values of the various parameters.

Be ions are implanted into Te‐doped Ga0.96Al0.04Sb layers grown by liquid‐phase epitaxy. Be distribution is analyzed from secondary‐ion mass spectrometry profiles and is found to be in good agreement with a computed simulation one. Hall‐effect measurements show a complete electrical activity of the Be‐implanted ions. Mesa devices are realized on the Ga0.96Al0.04Sb p+/Ga0.96Al0.04Sb n−/GaSb+ system: Be implantation leads to good quality junctions exhibiting homogeneous multiplication.

Ionization coefficients of holes and electrons (kp and kn) in Ga0.96Al0.04Sb have been derived from the variations of the photocurrent multiplication as a function of the reverse bias in Be‐implanted p+Ga0.96Al0.04Sb/n Ga0.96Al0.04Sb/n+ GaSb mesa diodes. Three wavelength values have been used for the illumination in order to obtain pure hole injection, nearly pure electron injection, and mixed injection. The kp and kn values thus determined for electric fields varying from 18 to 32 V/μm exhibit a high ratio value showing the interest of this material for avalanche photodiodes devices.

We have measured impact ionization rates in Ga1−xAlxSb at x=0 and 0.08. For these Al contents, the ratio values of the spin‐orbit splitting energy Δ to the energy gap Eg are, respectively, greater and lower than unity. We have determined that the ratio of the ionization coefficients kp/kn is greater than unity for both compositions and that it is much lower (kp/kn≊2) than the value (≳10) determined on our layers for x=0.04. Multiplication noise measurements confirm these results. The comparison to other published data show that the ionization in these antimonide compounds is not yet elucidated.

In order to characterize epitaxial or implanted antimonide layers on conducting substrates, we propose a simple method for the determination of the layer resistance and we discuss the limits of its validity in the following conditions of conduction between the layer and the substrate: ohmic type, generation-recombinaison type Dans le but de caracteriser des couches d'antimoniures epitaxiees ou implantees mal isolees d'un substrat conducteur, nous avons ete amenes a utiliser une methode simple de determination de la resistance de couche. Cette methode est decrite ainsi que sa limite de validite en supposant une conduction ohmique ou regie par la generation-recombinaison entre la couche et le substrat

The anisotropy of electron impact ionization rate as related to the band structure is experimentally established. At present, theoretical studies often attribute its dependence to the overlap integrals variations, alloy disorder effect or impact ionization process involving a second conduction band. We present a different numerical calculation of electron impact ionization probability in Ga1-x Al x Sb avalanche photodiodes (0≤x≤0.08). The ionization probability is calculated directly from the numerical evaluation of the matrix element including the full details of the first conduction band. It is found that the dependence of the electron ionization probability on the final states-density for impact ionization is very crucial compared with variations in overlap integrals or alloy disorder effect.

The calculation of the ionization probability and of the ionization coefficients of the holes of the spin split-off valence band in Ga1- x Al x Sb has been made for various compositions 0

Gold on n‐type Ga0.85Al0.15Sb devices were prepared and characterized. Current versus voltage (I‐V) and capacitance versus voltage (C‐V) measurements are discussed following the classical models of thermionic field emission and metal‐insulator‐semiconductor devices. The agreement between experimental I‐V results and thermionic field emission model is obtained for a barrier height value of 0.73 eV but the parameter N/m*e (N: carrier concentration; m*: effective mass; e: dielectric constant) involved in this model is ten times higher than the expected one, deduced from the doping level in the layer and from m* and e values in Ga0.85Al0.15Sb. In the case of the metal‐insulator‐semiconductor model, the comparison between the predicted and the experimental values of both the ideality coefficient n and the threshold V0 of C−2 versus reverse bias, allows to deduce the thickness of the surface insulating film δ≂45 A. As generally observed, the barrier height χ presented to electrons by the insulating layer is sma...

This paper presents a general method of calculation, allowing us to deduce the noise equivalent power in any type of avalanche photodiode. This method is checked by comparing numerical and analytical results for the case of a p‐i‐n junction. The calculation is applied to some Ga0.96Al0.04Sb diodes in order to estimate their performance and to deduce some trends for their optimization.

The liquid phase epitaxial growth of successive n- and p - Ga 0.96 Al 0.04 Sb layers is described. The equivalent doping level of the resulting junction is shown to be much lower than the limiting values of the n- and p-concentrations of individual homogeneous layers. A model is proposed to explain this interface concentration reduction. The photoelectrical properties of the devices realized from these p/n junctions are analysed; we show that the reverse current maybe as low as 2.5 uA for a 360 um diameter device at 300 K; the multiplication of the photocurrent I ph has been evaluated to be a value reaching 3 at a polarization range of – 20 V.

Nous décrivons la méthode de fabrication et les propriétés photoélectriques de trois types de diodes fabriquées à partir de couches de Ga0,96Al 0,04Sb déposées par épitaxie en phase liquide sur substrat n + GaSb. 1) Dans les jonctions p+ /n diffusées Zn la conduction inverse, avant avalanche, est dominée par l'effet tunnel (J(- 5 V) = 8,1 × 10-1 A/cm2). 2) Dans les jonctions p/n épitaxiées on observe une réduction du courant inverse (J(- 5 V) = 2,4 x 10 -2 A/cm2) qui peut être associée à une diminution du dopage effectif dans ce type de diode. Les rendements externes à 1,55 μm de ces deux dispositifs sont voisins de 0,27. 3) Les premiers dispositifs planar diffusés Zn sont de moins bonne qualité en relation probable avec des fronts de diffusion mal définis en bord de fenêtre. L'obtention d'un dispositif avalanche performant (NEP = 8,4 x 10-12 W/ √Hz) à partir des jonctions épitaxiées est conditionnée à la réduction des courants de fuite de surface.

In this paper we first present an analysis of current-voltage characteristics obtained in the dark and under illumination; this allows us to determine the cell parameters as well as their dependence on illumination intensity for different wavelengths. Capacitance measurements were carried out to give us more information.

We fabricated n-(indium tin oxide (ITO))/p-InP solar cells of 11% efficiency using the spray method to deposit ITO onto single-crystal p-type InP. For the atomic ratio Sn:In of 1:10 the optimized spray temperature is 450 °C. The various characterizations made on this type of device give results which are in good agreement with a buried homojunction model.

Ga0.96Al0.04Sb layers have been grown by liquid‐phase epitaxy on GaSb substrates at 400, 450, and 550 °C. The 450 °C growth leads to the best control of the layer’s quality. At 450 °C the natural p‐type doping of the layers is limited by the thermal acceptors ( p∼4×1016 cm−3) and the lowest reproducible uniform electron concentration obtained by Te compensation is n∼1016 cm−3. Electrical and photoelectrical properties of Schottky diodes and mesa Zn‐diffused homojunctions realized on these layers are described. They are strongly affected by surface effects attributed to the band bending of n‐type GaAlSb. Some parameters can be deduced from the various characterizations: the carrier lifetime in the space‐charge region of Zn‐diffused p+/n junctions, τ∼3×10−10 s; electron diffusion lengths in the as‐grown Ga0.96Al0.04Sb layer, Ln=5 μm, and in the Zn‐diffused layer, Ln=1.5 μm; and the hole diffusion length in the n‐compensated layers, Lp=1 μm.

Electron diffusion length measurements have been performed in p‐type InP by different methods: Surface photovoltage, spectrum analysis of the photocurrent in an Indium Tin Oxide/p‐InP diode, variation of the photovoltage in this diode versus reverse voltage, Electron Beam Induced Current measurements. The results are compared and discussed in detail. A double p‐type region model with different electron diffusion lengths has been proposed to explain the experimental results.

Fabrication parameters of n-SnO2/n-CdTe and SnO2/p-CdTe photovoltaic structures by the spray pyrolysis method are presented. Electrical and optoelectronic measurements of these structures have been made. A calculation of the photovoltaic output by means of a simple heterojunction model is reported. Good agreement between experimental and theoretical results for SnO2/n-CdTe structures has been obtained. Difficulties with and possibilities for improving the SnO2/p-CdTe solar cells are analysed.

Within a pilot plant framework, 25 Cu2S/CdS cells of back-wall structure were made in each run by the spray technique. The substrate of each cell is 2 cm × 2 cm × 0.2 cm . We first describe the fabrication process of each compound thin film; a review is then given of their chief optical and electrical properties. For 1 cm2 area and under 100 mW cm−2 illumination, we obtained a statistical mean efficiency of 6%, the best result being 7.4%. The variations in the cell parameters (ifI s , a, R s and R sh were studied as functions of illumination intensity. The photocurrent was computed and its variation is given as a function of the main parameters.

The discontinuities in the graphs of the electrical conductivity thermal variation have enabled the determination of the outline of the region where the α″ phase exists, for CuxTe single crystals with x between 1.985 and 1.84. In particular, it was able to be shown that there are two transformations, at 264°C and at 172°C, whatever the value of x. The low temperature measurements showed that other phase changes could exist around −25°C and −125°C.

Resume Differential thermal analysis has been used to study the phase diagram of the system CuS from 30°C to 500°C, the concentration measurements cover the range from Cu 1.78 S to Cu 2.1 S. In particular this study have enabled the explanation of the anomalous discontinuities in the graphs of the electrical conductivity thermal variation.

Differential thermal analysis has been used to study the phase diagramm of the CuTe system from 30°C to 600°C, the concentration measurements cover the range from Cu 1,84 Te to Cu 1,985 Te where the α″ phase exists. In particular this analysis completes a previous study of the electrical conductivity variation which was able to show the different phases transformations.

In this paper we present the electrical and optical characterization deduced from different series of Cu2S-CdS sprayed solar cells. The spectral responses are modelized in order to explain the junction formation process and the part played by CdS and Cu2S in this evolution.

Dans cet article nous montrons que dans les photopiles Cu2S-CdS (SAT) les lois de courants a l'obscurite et sous eclairement correspondent a des mecanismes, de conduction par effet tunnel. De plus en supposant l'existence d'une couche interfaciale limitee par des etats d'interfaces entre le Cu2S et le CdS, nous avons pu expliquer les resultats concernant les mesures de la capacite en fonction de la tension appliquee.

ITO/InP photodetectors and electroluminescent diodes have been fabricated spraying a ITO layer onto a single crystal p InP. The results of electrical and interface characterizations agree with a model of a buried homojunction. The maximum quantum efficiency reaches 0.9. The electroluminescence is correlated to the recombination on the acceptors in the p InP, the emitted light at 1.34 eV for a direct current of 0.1 A is 0.67 mW.

The realization of efficient photocells involving a semiconductor and I.T.O. window has recently received increased interest. We present here the properties of three types of such photocells obtained with three different semiconductors: n Si, p InP, n or p CdTe and a front ITO layer deposited by spray. The optical and electrical properties of our sprayed ITO layers are comparable to the best ITO films fabricated by more sophisticated methods (transmission ≃ 90%, square resistance = 10Ω for 0.5 μn thick film). Electrical and optical measurements such as dark I-V characteristics versus temperature, C-V characteristics, photocurrent spectral response, I-V characteristics under AM 1 illumination are compared for the three devices.

Evaluated performances of Ga0.96A10.04Sb avalanche photodetectorsHenri Luquet, Michele Perotin, Leone Gouskov, David Magallon, Alain Jean, Pierre SilvestreCentre d'Electronique de Montpellier (associe au C.N.R.S. - U.A. 391)Universite des Sciences et Techniques du Languedoc, Place Eugene Bataillon - 34060 Montpellier -cedex - FranceAbstract

In this paper, we present the experimental results on the transparency T and the square resistance RO of Indium Tin Oxide layer (ITO).We show the variation of T and RO with the thickness t of ITO layer. Then, we compute the influence of T and RO on the cell efficiency n; we deduce the optimal thickness in order to minimize losses introduced by the ITO layer.

Sulfur diffusion into p type Zn doped InP substrates is investigated in order to obtain efficient photocells. The heat treated substrates suffer a strong modification under the involved heat treatment, the doping level is increased, the luminescence is degraded and the photoelectrical parameters: diffusion length and lifetime of carriers exhibit inhomogeneous values. The diffusion follows the erfc law near the surface and leads to a plateau near the junction. Very good quality diodes have been obtained (dominated by diffusion conduction) with deep junctions. The behaviour of spectral responses is complex due to the diffusion length gradient. The best internal efficiency measured on a small mesa diode (∅= 560 μm) is 19.5%.

p and n GaSb layers have been grown on GaSb and semi-insulating GaAs substrates by Metal Organic Chemical Vapor Deposition (MOCVD) method ; the lowest doping levels obtained are : p = 2 x 1016 cm-3, n = 8 x 1015cm-3. P type Ga1-xInxAsySb1-y layers have also been fabricated by MOCVD with a composition insuring the photodetection at a wavelength of 2.5µm. The properties of the layers and of the as grown junctions are described.