The interfacial microstructures of lattice strained InxGal-xAs/GaAs multiple layer structures, that were grown by molecular beam epitaxy (MBE) on GaAs (100) substrates, have been investigated and characterised by transmission electron microscopy (TEM). A g3ii weak beam imaging technique has been used to study structural imperfections at the heterointerfaces. The morphology of rough heterointerfaces, which resulted from the growth of the InxGal-xAs layers (strained layer) either in a two dimensional (2D) or in a three dimensional (3D) growth mode via island formation, was imaged using this technique. A transition from 2D to 3D growth was found to occur at a certain critical layer thickness which decreased with increasing indium fraction. In thicker layers, dislocation complexes, which may have been caused bythe formation of islands, were also observed. These complexes were primarily composed ofstacking faults bounded by partial dislocations.

By analyzing in-situ strain relaxation measurements of GexSi1-x/Si(100) epitaxy in a Transmission Electron Microscope, we are able to quantify the fundamental parameters which describe strain energy relaxation via misfit dislocation introduction. Quantitative descriptions of misfit dislocation nucleation, propagation and interaction processes are derived. The numerical parameters obtained from these experiments are then incorporated into a predictive theoretical model of strain relaxation whichrelies only upon experimentally measured quantities. Good agreement between experiment and theory is obtained over a wide range of data.

The lattice misfit strain in an overgrown island is considered to be accommodated by twodistinctive domains; a pure coherency domain (ε domain) and a domain of misfit dislocations (δ domain). By introducing such two different constituents, the model predicts the transition condition from a “single phase” state (ε phase) to a “two-phase mixture” (ε+δ) as a function of misfit strain. Further, as in the chemical thermodynamics of a binary alloy system, energy vs. misfit strain diagrams allow us to understand possible existence of various metastable states which may be associated with an overgrowth.

We report the dynamic RHEED (reflection high energy electron diffraction) observation during Ge/Si(001) heteroepitaxy at various growth temperatures. The RHEED intensityanalysis and the in-plane lattice constant analysis reveal a growth fashion and lattice relaxation. Both of them depend strongly on growth temperature.

The valence band offset for the Si/Ge interface is studied using the local density functional approach with a superlattice geometry. The effect of non-abrupt interfaces is modeled by including an interface layer of Si5 Ge0 5 ordered in a interface unit cell. The change in valence band offset is less than 0.01 eV. For an abrupt interface, the offset is found to be a function of strain in the Ge. The interface dipole is proportional to the perpendicular strain parameter which yields an interface contribution to the energy of the strained epitaxial Ge layers. The equilibrium strain parameter in epitaxial Ge differs from that in biaxially compressed bulk Ge.

We have grown single and multi-layer epitaxial GexSi1−x/Si structures by RTPCVD on (100)Si substrates using GeH4 and SiH2Cl2 at 900°C and 1000°C with SiH2Cl2:GeHH4 ratios of 14:1 to 95:1 at 5 Torr. Plane view TEM micrographs indicate misfit dislocation free layers were grown for Ge concentrations of up to 13%. Misfit dislocation networks aligned along <110> were formed at the interface of films with higher Ge concentrations. Plane view TEM micrographs also showed dislocation loops at the interface. When the SiH2C12:GeH4 ratio used was less than 25:1, the GexSil−x layer grew by three-dimensional nucleation, resulting in a high density of defects.

The electron-beam-induced-current (EBIC) technique has been used to image dislocations and other defects at strained Si: Sil−xGex epitaxial interfaces and in overlying epitaxial layers grown by Limited Reaction Processing. Depending upon the bias conditions and test structure, one can distinguish between interface defects and those in overlying films. We have found that for a low density of misfit dislocations, a high quality (defect-free) overlying epitaxial layer can be grown, but for a high density of dislocations certain line defects propagate upwards in the overlying layers.

Raman scattering and x ray diffraction were used to study the effects of annealing on a Ge/Si superlattice that had been grown upon a Ge0.4Si0.6 alloy buffer layer which distributes the strain between the layers. Anneals above 910K caused substantial mixing at the Ge-Si interfaces. The interdiffusion coefficients obtained from the x-ray data were found to obey an Arrhenius relation with an activation energy of 3.1±0.2eV. Initial intermixing seems to be dominated by the diffusion of Si atoms into the Ge layers via a vacancy mechanism.

Interfacial roughness can be measured at buried interfaces using plan view transmission electron diffraction. The method relies on surface termination Bragg reflections and is applied to the Si/SiO2 system. In contrast to other methods, this does not require stripping of the SiO2 overlayer or projection assumptions. We find that thermal oxide interfaces are significantly flatter than previously supposed.

The Si/SiO2 interface has been extensively examined by a wide variety of techniques. A subset of these studies have focussed on the interfacial roughness and it has been shown that increased step density reduces electron mobility.[1, 2 ] Although supporting the correlation of mobility with step density, the data presented here shows thermally oxidized Si/SiO2 interfaces to be significantly flatter than previously assumed.

Optical properties of GaAs-Al0 5Ga0 5As multiple quantum wells affected by interface roughness have been investigated by timeresolved photoluminescence. The interface roughness affects on exciton dynamics is shown to be more complicated than those previously well studied line-width broadening of exciton transitions. A two-exponential decay of exciton luminescence and exciton peak shifting with increasing delay time have been observed. These observations have been successfully interpreted in terms of the interface roughness effects.

Defects and microstructures in a ternary GaAsxP−x compound have been studied by transmission electron microscopy. The compound was grown on a (100) GaP substrate by vapor phase epitaxial. Crystal growth striation contrast was detected in a TEM image. This contrast was explained by local compositional variation of As and P. The distribution of misfit dislocations in the interface region was also studied.

Whenever an atom of As is substitutionally replaced by a P-atom in a compound such as GaAs, due to the difference in ionicity, local puckering is effected by charge transfer. This paper deals with a calculation of the total energy stored, Eex = E(strain) + E(interface) = Es + Eint. For thick epilayers of GaP on GaAs, Eex is dominated by Es. However, for severalatomic layers of GaP on GaAs, the dominant stored energy is actually represented by the electrical dipole-dipole energy at the interface. The creation of dislocations may release the strain energy, it cannot affect the interface dipoleterm. Only inter-diffusion can lower the interface energy.

The recently developed techniques of pulsed laser atom probe microanalysis (PLAP) and position sensitive atom probe (POSAP) have been applied to the study of quantum well interfaces in samples that have also been well characterised by the more conventional techniques of TEM and STEM. These techniques have the potential for providing chemical information with a spatial resolution of better than 2nm, but the atom probe has the ability to independently resolve morphological and microchemical features of interfaces in three dimensions.

This paper presents results taken from GaInAs/lnP MOCVD-grown samples, comparing information on well composition, and on the chemical abruptness and morphological roughness of interfaces using complementary analysis techniques. We have concentrated on obtaining reliable quantitative data on the phosphorous content of the GaInAs wells and on the gallium and arsenic contents of the InP barrier layers.

The effects of thermal heat-treatment, N+ -ion, Ar+ -ion, γ-ray and electron-beam irradiations have been studied on MOCVD-grown ZnSe-ZnS strained-layer superlattices (SLSs) by means of low-temperature photoluminescence and X-ray diffraction measurements. As-grown SLS structure seems to be stable against the heat-treatment compared to ZnSe thin film, but after the defects are introduced in the SLS by irradiation, additional fluctuation at the interface between the ZnSe well and the ZnS barrier layers takes place. However, no significant intermixing and the changes of strain can be detected in the irradiated SLS.

We demonstrate that the use of vicinal (001) GaAs surfaces allows twin suppression in M.B.E. grown (111) CdTe. High Resolution Electron Microscopy is used to investigate the atomic structure of and the defects present at the interfaces, as a function of cutting angle and surface preparation. A model is presented that takes into account possible coincidences of facets in CdTe and GaAs in order to explain twin suppression, layer misorientation and the type of interfacial defects.

We describe two methods for producing thermally stable high resistivity layers in GaAs-AlGaAs heterostructures. These rely on the interaction of implanted ions with dopant impurities already present in a buried layer in the heterostructure. In the first case, oxygen implanted at a concentration above that of the acceptors in p-type GaAs is shown to create thermally stable, highresistivity material only in the case of Be-doping in the GaAs. The effect is not seen for Mg-, Znor Cd-doping. Similarly there is no apparent interaction of 0 with n-type dopants (S or Si). The Be-O complex in p-type GaAs is a deep donor, creating material whose sheet resistivity shows a thermal activation energy of 0.59 eV. In the second case oxygen implantation into n+ AlGaAs, followed by annealing above 600°C, creates a deep acceptor level that compensates the shallow donors in the material. Temperature dependent Hall measurements show the resistivity of the compensated AlGaAs has a thermal activation energy of 0.49 eV, in contrast to a value of 0.79 eV for non-induced damage compensation.

A GaAs p/n junction grown on a n-Ge substrate has an anomalous photoresponse that includes a quantum yield response starting at the 0.7-eV band edge of Ge. In terrestrial sunlight, its I-V characteristic has an anomalous “notched” shape that is progressively removed by increasing the infrared light content. The I-V is well modeled by a space-charge-limited-current diode theory with a GaAs/Ge interface defect density of 1.92 (1012) cm−2 eV−1 at 0.4 eV below the conduction band edge. Similar defect densities have been reported for GaAs/oxide interfaces and for a GaAs p/n junction interface specially selected for high defect densities.

Isolated silicon epitaxy (ISE) is a proven method of producing single crystalline silicon-on-insulator (SOI) material with excellent electrical properties. The presence of the remaining isolated dislocation trails in the epitaxial silicon has led to this investigation of the crystallinity throughout the ISE SOI layer and across the isolated dislocations. The structural perfection of these layers has been examined by defect etching, Nomarski optical microscopy, electron channeling patterns, and with more sensitivity using double crystal synchrotron X-ray diffraction and topography. Defect etching reveals the dislocation density within the layers of production ISE SOI material to be ~5×l0 5 /cm2. Electron channeling pattern techniques have reached the resolution limit of angular orientation resolution for the isolated silicon layer. Finally, synchrotron studies have shown that orientation homogeneity across 5" wafers are preserved to 0.006° and the variation in orientation across the defect trails to be, in general, less than 10 arcsec (0.003°), indicating single crystalline ISE SOI production material.

Photoinjection of electrons into silicon dioxide in metal-oxide-semiconductor (MOS) capacitors with 3.5 eV light is shown to create interface states with no apparent hole trapping precursor. The creation rate of these interface states depends strongly upon whether injection is from the gate metal or the silicon substrate, and on the forming gas annealing sequence used to passivate growth-induced interface states. A mechanism involving electron-induced release of hydrogen in the oxide is consistent with some aspects of the data.

Metal-Oxide-silicon (MOS) capacitors have been fabricated on CFb reactive ion etched silicon (n and p types) in order to study the defects at the Si-Si02 interface and in the bulk of the substrate, produced by the combination of reactive ion etching (RIE) and oxidation. Bulk defects and fast interface states are analysed by Deep Level Transient Spectroscopy (DLTS) and the slow interface states in the oxide layer near the interface are probed by Tunnel-DLTS. A density of fast interface states in the range 1010-1011 cm−2 eV−1 is observed for capacitors (both n and p types) fabricated with either dry or wet oxidations, and is probably due to disrupted or strained bonds at the Si-SiO2 interface. The observation of bulk defects in the wet-RIE oxide samples but not in the dry-RIE oxide samples may be related to the shorter oxidation time for wet oxides (31mn) compared to dry oxides(190mn) and explained by a greater annealing of RIE induced defects during the dry oxidation. The bulk traps are identified to be related to carbon contamination, in SiC form, introduced during RIE. Finally, an increase of the slow interface states density is observed for the n-type dry oxide samples.