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The properties of GaAsSbN and GaAsSb layers grown by liquid-phase epitaxy on n-GaAs substrates were investigated in a comparative plan with a view of their possible application in multi-junction solar cells. To avoid non-uniformity effects in the composition of these compounds with two or three different group-V volatile elements, the crystallization was carried out from finite melt with a thickness of 0.5 mm at low (

We report uniform Type-II GaInAsSb/InP UTC-PDs, and compare their performance to devices fabricated with GaAsSb uniform and graded (composition and doping) absorbers of the same thickness. The quaternary UTC-PDs show a transit limited bandwidth of 274 GHz in contrast to 107 and 185 GHz for uniform and graded GaAsSb absorber UTC-PDs. Because the uniform quaternary and ternary UTC-PDs only differ in their absorber material, the findings conclusively demonstrate enhanced transport in GaInAsSb. Performance comparison to GaInAs-based devices from the literature suggest that GaInAsSb is a superior absorber material for λ = 1.55 μm high-speed photodetectors. Additionally, the external responsivity of the GaInAsSb UTC-PDs (0.094 A/W) is ~34% higher than the GaAsSb PDs (0.070 A/W). This is the first demonstration of a quaternary GaInAsSb absorber in UTC-PDs., Journal of Lightwave Technology, 39 (7), ISSN:0733-8724, ISSN:1558-2213

A type-II (with broken bandgap) W-shaped nano-heterostructure having layers combination of AlSb, InAs and GaAsSb compound semiconductors has been proposed which can be utilized as high intensity lasing source in MIR (mid infrared region). For this heterostructure, a multiband band k.p Hamiltonian has been simplified to compute the required carrier’s wavefunctions, their subband structures and matrix dipole elements accountable for the probabilistic transitions which results into the high optical gain. For 2-D charge carrier density of 1.5 × 1012 cm−2, the computed results confirm that only the light hole (LH) subbands take part in optical transition in order to produce the high optical gain of the order of ~8850 /cm which corresponds to ~5.2 µm. Keeping in view its high optical gain at ~5.2 µm, the proposed type-II AlSb/InAs/GaAsSb heterostructure can be useful in the environmental monitoring, particularly important for sensing the CO2, CO and NO toxic gases available in the polluted environment. Moreover, this type-II heterostructure can also play an important role in traditional applications such as industrial, medical, MIR spectroscopy, and telecommunications applications which require ~5200 nm wavelength.

During the last few years, there has been renewed interest in the monolithic integration of gold-free, Ternary III–As Antimonide (III–As–Sb) compound semiconductor materials on complementary metal-oxide-semiconductor (CMOS)—compatible silicon substrate to exploit its scalability, and relative abundance in high-performance and cost-effective integrated circuits based on the well-established technology. Ternary III–As–Sb nanowires (NWs) hold enormous promise for the fabrication of high-performance optoelectronic nanodevices with tunable bandgap. However, the direct epitaxial growth of gold-free ternary III–As–Sb NWs on silicon is extremely challenging, due to the surfactant effect of Sb. This review highlights the recent progress towards the monolithic integration of III–As–Sb NWs on Si. First, a comprehensive and in-depth review of recent progress made in the gold-free growth of III–As–Sb NWs directly on Si is explicated, followed by a detailed description of the root cause of Sb surfactant effect and its influence on the morphology and structural properties of Au-free ternary III–As–Sb NWs. Then, the various strategies that have been successfully deployed for mitigating the Sb surfactant effect for enhanced Sb incorporation are highlighted. Finally, recent advances made in the development of CMOS compatible, Ternary III–As–Sb NWs based, high-performance optoelectronic devices are elucidated.

Es war Ziel dieser Arbeit den Zusammenhang zwischen optischen und strukturellen Eigenschaften verschiedener, funktionalisierter Halbleiterhetherostrukturen zu untersuchen. Dazu wurden die optischen Eigenschaften etlicher Ga(N,As,P) Heterostrukturen, die bei verschiedenen Temperaturen hergestellt und mit verschiedenen Prozessen getempert wurden, untersucht. Zusätzlich wurden unterschiedliche Probenstrukturen im Hinblick auf verschiedenen Qunatenschichtdicken und unterschiedliche borhaltige Barrieren, untersucht. Um die optischen Eigenschaften der Proben aufzudecken wurde eine Vielzahl an verschiedenen Methoden verwendet, einschließlich Dauerstrich-PL, zeitaufgelöster PL, Anregungsspektroskopie und Ramanspektroskopie. Zusammenfassend bleibt festzuhalten, dass die Wechselwirkung von optischen und strukturellen Eigenschaften der Materialsysteme Ga(N,As,P) / Si, (Ga In) As / Ga(N,As) und (Ga In) As / Ga (As,Sb) untersucht wurde. Die optische Spektroskopie erwies sich dabei als nützliches Werkzeug um die Materialien nichtdestruktiv zu untersuchen und viele neue Erkenntnisse zu erhalten. Somit war es möglich ein tiefergehendes Verständnis der Wechselwirkung von Quantenfilmstruktur und zugehörigen optischen Eigenschaften zu erhalten., Semiconductor lasers are widely used in all areas of everyday life. They can be found in personal computers, TVs, CD and DVD players, printers and laser pointers, just to name a few. However, a very important field they are used in is optical communication. This thesis tackles two of the major challenges in this field. First, on short distances, i.e. on-chip or chip-to-chip, data is usually transmitted using electrical wires. However, the interconnects between different parts of the processor are actually the limiting factor for device performance. Additionally, the power dissipated due to the interconnects on a chip is significant. Therefore, it is reasonable to consider other approaches to transfer data on-chip and between chips. One possibility is changing the means of data transfer from electrical to optical providing faster interconnects and a higher energy efficiency. To do so, efficient and stable lasers on silicon substrates are needed. Even though optically driven silicon lasing has been demonstrated in the past, silicon is not the first choice because of its indirect band gap. Using other semiconductor materials such as Ga(N,As,P), which is investigated here, is a reasonable choice for optoelectronic integration for the following reasons. For As contents exceeding 70%, the quaternary Ga(N,As,P) is a direct band gap semiconductor that can be grown lattice matched to silicon using standard MOVPE techniques. Furthermore, laser operation at up 150 K - and at RT on GaP substrates - has already been demonstrated. However, from this it becomes clear that further device improvements are necessary to reach RT lasing. This thesis investigates the interplay of optical properties, alloy disorder and structural changes in Ga(N,As,P)/Si heterostructures to get a better understanding of this material. The influence of several growth and annealing parameters and processes on the optical properties is investigated as well as the influence of different sample structures and heterostructure layouts. To reveal the optical properties photoluminescence spectroscopy experiments are performed. In conjunction with structural investigation by Transmission Electron Microscopy the role of structural changes due to growth and annealing procedures and their influence on the optical properties is revealed and discussed. These results not only yield a better understanding of the complex interplay of growth parameters/structural design and optical response, but also can be used as feedback for subsequent growth of further samples leading to better device performance. Furthermore, the band offset, which is a critical parameter of a heterostructure for laser operation, is determined experimentally for the first time. The second part of this thesis deals with light sources for long-range optical communication, which is usually done using optical fibers. These optical fibers are operated best at 1.3 µm or 1.55 µm where the losses are minimal and the dispersion is closest to zero. Semiconductor lasers operating in this wavelength regime are usually made of (Ga,In)(As,P) or (Al,Ga,In)As on InP substrates. Their efficiency is somewhat poor as much of the pump power is converted to heat due to non-radiative processes. One of the most dominant processes is the Auger recombination, where the recombining electron and hole transfer their energy to another charge carrier as kinetic energy rather than creating a photon, which is emitted. To overcome these issues it is helpful to use type-II devices where the recombining electrons and holes are confined in different materials and spatially separated. In such a device the optical properties can be optimized while the Auger losses can be lowered. Additionally, such systems offer more degrees of freedom for device design as more and different materials can be used. In this thesis are investigated (Ga,In)As/Ga(N,As) heterostructures, which are used as type-II light sources in the range of 1.3 µm to 1.55 µm. Furthermore, (Ga,In)As/Ga(As,Sb) heterostructures serving the same purpose are investigated. Particular attention is paid to the influence of the interface these type-II devices inevitably have. Especially, reports on the influence of interfaces on the optical properties of these materials are lacking in the literature. The type-II PL is used as a non-destructive probe for the optical properties of such systems and their changes upon changing the interfaces. It is aimed to reveal the influence of the internal interfaces on the cw-photoluminescence as well as on the recombination dynamics and charge carrier (re-)distribution in the heterostructures. In particular, the latter ones are scarcely investigated in the literature. The optical properties will be correlated with different interface properties such as thickness and morphology. The influence of the interface on disorder is also investigated. Finally, the measurements are also used to determine the Ga(N,As)/GaAs and Ga(As,Sb)/GaAs band offsets, which are disputed in the literature.

This paper presents Si/SiGe:C and InP/GaAsSb HBTs which feature specific assets to address submillimeter-wave and THz applications. Process and modeling status and challenges are reviewed. The specific topics of thermal and substrate effects, reliability, and HF measurements are also discussed.

Capping InAs/GaAs quantum dots (QDs) with a thin GaAsSb layer alters the QDs structural properties, leading to considerable changes in their optical properties. The increase of the Sb content induces a redshift of the emission energies, indicating a change in the buried QDs shape and size. The presence of well-defined ground- and excited-state emission bands in all the photoluminescence spectra allow an accurate estimation of the buried QDs size and shape by numerical evaluation and tuning of the theoretical emission energies. For an Sb content below 14%, the QDs are found to have a type I band alignment with a truncated height pyramidal form. However, for higher Sb content (22%), the QDs are present in a full pyramidal shape. The observed behavior is interpreted in terms of increasing prevention of InAs QDs decomposition with increasing the Sb content in the cap layer.

International audience; In this work, Molecular Beam Epitaxy (MBE) grown tunnel junctions (TJs) based on GaAs(Sb)(In) materials are experimentally and numerically studied. From simple GaAs TJs grown with various n-doping levels, we develop a semi-classical interband tunneling model able to quantify the magnitude of the tunneling current density, which shows that direct interband tunneling is the predominant tunneling mechanism in GaAs tunnel junctions instead of trap-assisted-tunneling mechanisms. Numerical simulations based on non equilibrium perturbation theory through Non Equilibrium Green's Functions (NEGF) and a multi-band kp hamiltonian that includes both gamma and L valleys were performed by the IM2NP (Marseille) and confirmed this result. In order to further improve the performance of the TJs, we are fabricating a type II tunnel heterojunction based on GaAsSb and InGaAs materials.

This work reports on the benefits from using thin GaAsSb capping layers (CLs) on InAs/GaAs quantum dot (QD) solar cells. The application of such CLs allows the tunability of the QD ground state, switching the QD-CL band alignment from type I to type II for high Sb contents and extending the photoresponse beyond 1.5 µm. Two different structures with ~10% and ~20% Sb contents in the CL (type-I and type-II band alignments, respectively) are explored, leading to efficiency improvements over a reference InAs/GaAs QD solar cell of 20% and 10%, respectively. In general, a significant increase in short-circuit current density (Jsc) is observed, partially due to the extended photocurrent spectrum and the additional contribution of the CL itself. Particularly, for a moderate Sb content, an improved carrier collection efficiency is also found to be a main reason for the Jsc increase. Calculations from an 8×8 k·p method suggest the attribution of such an improvement to longer carrier lifetimes in the wetting layer-CL structure due to the transition to a type-II band alignment. Open-circuit voltages (Voc) exceeding that of a reference QD solar cell are demonstrated under light concentration using GaAsSb CLs, which proves that the Voc is not limited by the low bandgap CLs. Moreover, the highest value is obtained for the high Sb content type-II structure, despite the higher accumulation of strain and the lower effective bandgap. Indeed, the faster Voc increase with light power found in the latter case leads to an Voc even larger than the effective bandgap., We acknowledge the Spanish MICINN-MINECO for funding through project MAT2013-47102-C2-2-R. JMLL and IA acknowledge the financial support of the Comunidad Autónoma de Madrid (Grant S2013/MAE-2780), TEC2015-64189-C3-2-R (MINECO/FEDER) and MINECO (Grant AIC-B_2011-0806).

International audience; With the continued maturation of III-V nanowire research, expectations of material quality should be concomitantly raised. Ideally, III-V nanowires integrated on silicon should be entirely free of extended planar defects such as twins, stacking faults, or polytypism, position-controlled for convenient device processing, and gold-free for compatibility with standard complementary metal-oxide-semiconductor (CMOS) processing tools. Here we demonstrate large area vertical GaAsxSb1-x nanowire arrays grown on silicon (111) by molecular beam epitaxy. The nanowires' complex faceting, pure zinc blende crystal structure, and composition are mapped using characterization techniques both at the nanoscale and in large-area ensembles. We prove unambiguously that these gold-free nanowires are entirely twin-free down to the first bilayer and reveal their three-dimensional composition evolution, paving the way for novel infrared devices integrated directly on the cost-effective Si platform.

With the continued maturation of III–V nanowire research, expectations of material quality should be concomitantly raised. Ideally, III–V nanowires integrated on silicon should be entirely free of extended planar defects such as twins, stacking faults, or polytypism, position-controlled for convenient device processing, and gold-free for compatibility with standard complementary metal–oxide–semiconductor (CMOS) processing tools. Here we demonstrate large area vertical GaAsxSb1–x nanowire arrays grown on silicon (111) by molecular beam epitaxy. The nanowires’ complex faceting, pure zinc blende crystal structure, and composition are mapped using characterization techniques both at the nanoscale and in large-area ensembles. We prove unambiguously that these gold-free nanowires are entirely twin-free down to the first bilayer and reveal their three-dimensional composition evolution, paving the way for novel infrared devices integrated directly on the cost-effective Si platform.

Short wavelength infrared (SWIR) and mid wavelength infrared (MWIR) photodetectors have applications in areas such as chemical sensing, gas monitoring, medical diagnostics, infrared imaging and free-space communications. Mercury Cadmium Telluride (HgCdTe) is the predominant material system used in SWIR, MWIR and long wavelength infrared (LWIR) applications. However, HgCdTe often suffers from poor material uniformity and low yield. Comparable performance can be achieved on GaSb substrates with high quality InAs/GaSb strained-layer superlattices, but significant cooling is required to achieve high detectivity performance. Indium Phosphide (InP) based InGaAs/GaAsSb type-II quantum wells photodiodes are the promising candidates for the detection in SWIR and MWIR region, especially at room temperature. These photodiodes can take advantage of mature material and device technology of InP material system. In this dissertation, I study these InP based type-II quantum wells photodiodes theoretically and experimentally. Six-band k•p modeling was used to design these type-II quantum well structures. It is found that in order to maximize the transition wavelength and wave function overlap under strain compensated condition, the thickness of the InGaAs layer should be larger than that of the GaAsSb layer, and the GaAsSb layer should be compressively strained, while InGaAs layer should be tensile strained. Both lattice matched and conventional strain compensated type-II quantum wells photodiodes are designed and studied experimentally in this dissertation. How the performance of these type-II photodiodes changes as the detection wavelength increases is studied by comparing the performance of both photodiodes. The research has shown that the device with 100 pairs of 7nm In0.34Ga0.66As/5nm GaAs0.25Sb0.75 strain compensated type-II quantum wells absorption region has an optical response out to 3.2µm, while the device with 100 pairs of 7nm In0.53Ga0.47As/5nm GaAs0.5Sb0.5 lattice matched type-II QWs absorption region has an optical response out to 2.7µm. The strain compensated devices show detectivities of 1.4×109cm•Hz1/2•W-1 at λ=2.7m at 290K and 1.5×1010cm•Hz1/2•W-1 at 200K. For λ=3.0m, the detectivity D* is 2.0×108 cm•Hz1/2•W-1 at 290K and increases to 1.0×109 cm•Hz1/2•W-1 at 200K. They are the first 3µm results demonstrated on InP substrate, using interband transition without lattice mismatch layers. Moreover, in order to further extend the detection wavelength, the new strain compensated InGaAs/GaAsSb QWs PIN photodiode is studied, which can lead to much longer detection wavelengths for similar GaAsSb compositions based on the modeling. This new strain compensation concept is demonstrated experimentally to have a cut-off wavelength similar to that of conventional strain compensated sample but with lower Sb composition in the GaAsSb layer. In addition, the carrier transport mechanism in the type-II quantum wells is studied in order to improve the carrier collection efficiency, and it is found that the thermionic emission is the dominant way for the photo generated electrons to get out of the quantum wells.

International audience; In this paper, a fully passivated InP/GaAsSb/InP DHBT on InP substrate with excellent DC and RF performance is developed. The epi-layers are grown by the MOCVD technique, with a base layer of 25nm and a collector layer of 130nm. The emitter width of the transistor is 0.35μm and the base contact is 0.3μm wide. The base and emitter contacts present an excellent contact resistivity. The current gain of the 0.35×5μm2 transistor is equal to 21 and the breakdown voltage is equal to 4V. The current gain cut-off frequency and the unilateral gain cut-off frequency are over 300 GHz and 380 GHz respectively. The transistor is fabricated in an industrial environment at OMMIC foundry.

Metastable GaAs(1-y)Sb(y) with 0.22 < y < 0.70 has been grown pseudomorphically strained on (001) InP substrates using metalorganic chemical vapor deposition. The Sb concentration and layer thicknesses, ranging from 24 to 136 nm, were determined by high resolution x-ray diffraction (HRXRD) measurements. Low-temperature photoluminescence (PL) spectroscopy revealed spatially indirect band-to-band emission of electrons localized in the InP and holes in the GaAs(1-y)Sb(y). At increased excitation power densities samples with layer thicknesses above 65 nm showed, also, spatially direct PL across the band gap of the strained GaAs(1-y)Sb(y). From the PL data the band gap energy and the band offsets of GaAs(1-y)Sb(y) relative to InP were derived and compared with the predictions of the Model Solid Theory.