The anodic etching of n+-type GaAs (100) substrate in HCl aqueous solution has been investigated experimentally using an in situ current–voltage J (V) and capacitance–voltage C (V) measurements. In situ current–voltage, J (V), characteristics of the n+-GaAs/HCl interface exhibit the presence of three potential regions, which are attributed to different reaction mechanisms between HCl and n+-type GaAs surface. Also, current peaks appear in the J (V) characteristics which delimit the different potential regions. According to the Mott–Schottky relation, the characteristic C−2 (V) exhibits the presence of two linear regions separated by a shoulder at about 1.15V. This shoulder indicates the formation of porous GaAs/HCl interface. Scanning electron microscopy (SEM) images shows that GaAs etched in HCl can produce various surface morphologies depending on the anodization current density. Reasonable assumptions on the dissolution mechanisms according to the variety of morphologies are given.

We have studied the structural and the optical properties of self-assembled GaInAs islands grown on AlInAs/InP (113)A and B oriented surfaces. The samples were grown by metalorganic chemical vapor deposition (MOCVD) and investigated using transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). It is found that the (113)B orientation of InP substrates allows to obtain disk-shaped GaInAs structures with a good size-homogeneity and repartition. On contrary, the GaInAs islands grown on the (113)A orientation have a considerable anisotropic shape, the islands are more elongated along the [01 (1) over bar] direction. Moreover, the GaInAs islands grown on the(113)B surface exhibit higher luminescence efficiency and a reduction in the photoluminescence spectrum linewidth compared with those grown on the(113)A surface. (C) 2000 Elsevier Science S.A. All rights reserved.

InP homoepitaxial layers and heteroepilayers of InP grown on (001) and (111)B surfaces of GaAs substrates by metalorganic chemical vapor deposition, have been investigated using time-resolved photoluminescence spectroscopy. In this study, we have focused on the intrinsic transitions. The measured decay-time for the heteroepitaxial layers of InP exhibited the same temperature dependence as the thermal quenching. The decrease of the decay-time as the temperature increase is attributed to the non-radiative processes, which are thermally activated. It is shown, by comparison with InP homoepitaxial layers, that the PL decay-time for InP on both (111)B and (001) surfaces of GaAs substrates is decreased. The reduction of the measured decay-time is considered to be due to the additional non-radiative processes arising from the threading dislocations. Compared with the InP on GaAs(001), the heteroepilayers on GaAs(111)B substrates exhibited a significant increase in the decay time as a result of the reduction in the threading dislocations density.

Heteroepitaxial InP layers were grown under the same growth conditions by metalorganic chemical vapor deposition on (001), (111)A, and (111)B surfaces of GaAs substrates. The heteroepilayers were studied by transmission electron microscopy, high-resolution x-ray diffraction, low-temperature photoluminescence, and low-temperature photoluminescence excitation. It is demonstrated that good quality InP epitaxial layers can be grown on GaAs substrates. Since layers and substrates have the same crystal structure, but different lattice parameters (aGaAs=5.6535 Å, aInP=5.8687 Å), the accommodation at the interface may occur by the formation of misfit dislocations parallel to the heterointerface. A remarkable reduction of the threading dislocation density for the (111) orientation and a decrease in the full width at half maximum values of the x-ray diffraction peaks were obtained. These results signify a dramatic crystalline improvement due to the reduction of the dislocation density using (111)-oriented GaAs substrates. The efficient photoluminescence and the full width at half maximum of the exciton peak compared with that of InP homoepitaxy show that good quality InP epilayers can be obtained on (111)-oriented GaAs substrates. The strain relaxation was investigated by high-resolution x-ray diffraction, and low-temperature photoluminescence excitation. The difference between the optical and the x-ray diffraction results is attributed to the thermoelastic strain due to the difference in the thermal expansion coefficients between epilayers and substrates.

In this work, we investigate heteroepitaxial layers of InP with various thicknesses grown by metalorganic chemical vapor deposition on (111)B surfaces of GaAs substrates. We evaluate the heteroepilayers using low temperature photoluminescence (PL) and we discuss the dependence of the PL spectrum on temperature for the thick epilayer. We determine the residual strain for the various layer thicknesses with photoluminescence excitation spectroscopy. The strain is due to different lattice constants of layer and substrate material and is relaxed by the nucleation of misfit dislocations during growth. This relaxation process depends on substrate orientation, layer thickness and growth conditions.

Heteroepitaxy of InP on GaP by low pressure metalorganic chemical vapor deposition is reported. The samples have a mirror-like surface as seen by the naked eye. The photoluminescence excitation measurements demonstrate that the heteroepilayers are under biaxial compressive strain in the surface parallel direction. The efficient photoluminescence and the full width at half maximum of the photoluminescence exciton peak for the 5000 Å thick layer compared with that of InP homoepitaxy show that high-quality InP on GaP (1 1 1)B oriented substrates can be obtained. These results are superior to those reported previously for the InP/Si.

Boron difluoride (BF2+) ions implantation through protecting oxide films was investigated to understand the behaviour of fluorine in damaged region under rapid thermal annealing (RTA) as well as in attempt to form shallow p(+)/n junctions. The implants redistribution profiles as a function of annealing temperatures and time have been monitored by the secondary ion mass spectrometry (SIMS). Implantation induced point-defects are detected by means of deep level transient spectroscopy (DLTS) technique. The effects of both fluorine and the RTA ion-implant damage annihilation on the transient enhanced boron diffusion are investigated. In particular, the fluorine segregation behaviour near the post implantation disturbed/crystalline interface, resulting in clustering and void formation, as well as near the initial oxide/crystalline silicon is closely related to used technological data.

Single crystals of lithium niobate were implanted at room temperature with 20 keV protons at fluences ranging from 5 x 10(16) H+/cm(2) to 2 x 10(17) H+/cm(2). Rutherford Backscattering Spectrometry in channeling geometry (RBS-C) performed at three beam energies (1, 1.5, and 2 MeV) and subsequent analysis of the energy dependence of the dechanneling cross section enabled us to show the predominant induced lattice defects are likely of a 'point' nature. Electron microscopy investigations also support this assumption.

The effect of Thermal Cyclic Growth (TCG) combined with a Thermal Annealing Cycle (TAC) to reduce dislocation density in GaAs/Si layers grown by low pressure OMCVD and the first step growth have been studied by TEM and HRTEM. A structure of one symmetric grain boundary has been examined by HRTEM and image simulation.

We have studied the early stages of growth of GaAs on Si (001), misoriented by 4° towards [110], by migration-enhanced epitaxy (MEE) in a molecular beam epitaxy (MBE) system. We present results using in situ and ex situ analyses, reflection high-energy electron diffraction (RHEED), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron diffraction (XPD) and X-ray double crystal diffractometry (DCD) performed at each stage of growth. We show that the nucleation by MEE induces a surface roughness decreasing as the layer becomes thicker. XPD experiments at the onset of the growth show a stoichiometric GaAs without antiphase domains. The relaxation of stress for the layers deposited at low temperature (300°C) occurs via partial dislocation migration developing between them, stacking faults and microtwins. The post annealing of films with thicknesses less than 60 nm drives the formation of three-dimensional islands on the silicon surface. These islands develop (114) facets in the [11¯0] direction where the Ga migration is greater. The height over the base ratio of these islands is uniform and from Bauer's relation, we calculate the interface energy which can be correlated to the strain energy due to the dislocations near the interface. There are two reasons for the restruction of the surface. First, from a thermodynamical approach including surfaces and interface energies of the GaAs/Si system, we can demonstrate that the growth of GaAs/Si is a three-dimensional Volmer-Weber growth. Second, the bulk energy due to the compressive strain of a continuous pseudomorphic GaAs film is higher than that of an islanding GaAs where relaxation from the free surfaces of the islands occurs. The post annealing of films with thickness higher than 60 nm has a smoothing effect and can give a perfect two-dimensional (001) surface. Growth at higher temperatures (580°C) suppresses plane defects, creates a Lomer dislocation network at the interface and induces the 60° dislocations in the bulk. We perform X-ray DCD experiments on 90 nm thick layers. We observe, before annealing a compressive biaxial stress of about −1.9×108Pa which is the driving force for the elimination of the plane defects.

The fist step growth of MOCVD GaAs/InP is studied using Transmission Electron Microscopy. We show that a complete coverage occurs for layers as thin as 65 angstrom grown at 450-degrees-C. When the thickness increases and after a 700-degrees-C annealing during 5 mn, the layers are more relaxed and the planar defects density decreases clearly, but unfortunatly thick epilayers (550 angstrom) are less smooth than thinner ones. So, the optimum epilayer thickness realising the compromise between complete surface substrate coverage, defect density and surface roughness was found to be in the order of 150 angstrom.

A characterization study of GaAs layers grown by metal-organic chemical vapour deposition (MOCVD) on silicon substrates is presented, based on high resolution transmission electron microscopy, secondary ion mass spectroscopy, admittance technique measurements (current-voltage, capacitance-voltage, capacitance and photocapacitance spectroscopy, deep level transient spectroscopy (DLTS) and photoluminescence (PL) spectroscopy in the near band gap and near infrared region). We have analysed the initial stage of growth and the influence of growth parameters as GaAs/AlAs superlattices (SLs) at different distances from the GaAsSi heterointerface in the buffer layer or post-growth thermal annealing or selective epitaxy on the reduction of dislocation density, on the silicon distribution, on the deep defect levels and on the coplanar tensile strain in the active layer. This study shows an improvement of the material quality in the dislocation density decrease due to GaAs/AlAs SLs grown directly on the initial prelayer, or post-growth annealing or selective epitaxy. DLTS measurements reveal deep electron traps in the range 0.5–0.7 eV below the CB induced by dislocations due to the heteroepitaxy. For the first time we observe deep hole centres in the range 0.4–0.5 eV above the top of the valence band, which could be involved in the reduction of the minority carrier lifetime. We discuss their origins due to silicon incorporation in the GaAs layer on the basis of capacitance and photoluminescence experiments. PL shows the increase of strain with post-growth annealing. Finally the improvement in the quality of the layers is pointed out on the basis of double heterostructure (GaAlAs/ GaAs/GaAlAs) characteristics.

We present a complete characterization study of GaAs/Si heteroepitaxial layers grown by metalorganic chemical vapor deposition (MOCVD) at 750C using the two-step method. High resolution transmission electron microscopy secondary ion mass spectroscopy deep level transient spectroscopy (DLTS) and photoluminescence (PL) spectroscopy have been performed to study the initial stage of growth misfit and threading dislocations Si diffusion and the deep levels in the GaAs layer. We describe the influence of GaAs/AlAs superlattices in the buffer layer on the decrease of dislocation density and on Si diffusion from the substrate and the existence of deep electron traps induced by the heteroepitaxy. DLTS reveals hole traps attributed to Si incorporation on the basis of PL measurements which could contribute to the reduction of the minority carrier lifetime. We also show an improvement of the layer quality by the use of selective epitaxy.

We report a study of metalorganic vapour phase epitaxy (MOVPE) grown GaAlAs/GaAs double heterostructures on Si substrates. The main part of this work deals with the influence of post growth annealing conditions on cathodoluminescence (CL) efficiency, defect reduction, Si distribution over the structure, and interfaces state. It has been found by 300 K cathodoluminescence measurements that treatment at high temperature up to 900°C reduces defect and deep level transitions giving rise to larger zones of high near band edge (NBE) emission luminescence in contrast to those observed on unannealed samples. Such improvement has been confirmed by transmission electron microscopy and luminescence decay measurements. Carrier life times as 6 ns have been measured indicating a ten fold increase after annealing.