It is shown that interfacial defects are characterised by combinations of symmetry operations, one from each of the adjacent crystals. This approach demonstrates that the variety of possible interfacial defects is broader than had been previously recognised, and includes disclinations and dispirations in addition to dislocations. The condition of the initial substrate surface is shown to have a very important influence on the character and stability of interfacial defects.

The equilibrium configurations of monolayer films on crystalline substrates have been investigated using molecular dynamics techniques. Misfit dislocation densities are found to differ from those predicted by elasticity theory, because of the more realistic interatomic potential employed in the simulations (Lennard-Jones), and the absence of constraints on atomic positions. Two distinct dislocation core structures are observed, with a discontinuous transition between the two as the external conditions are changed. Shockley partial dislocations are found to be stable for a large range of misfits in the case of FCC (001) substrates, and recently an experimental observation of these dislocations was reported. The stability of monolayer films relative to the formation of three-dimensional clusters is also considered.

The perfection and compositional stability of alternate monolayer compounds (AMC) structures deposited by molecular beam epitaxy as a function of several crystal growth parameters are reviewed. By using the (GaAs)1 - (AlAs)1 AMC structure as a prototype system, the effects of substrate temperature, and orientation on the AMC ordering are presented. Conditions for producing new superlattice architectures are discussed.

A study of defects that are observed in Si MBE layers under certain growth conditions is reported. Optical microscopy examinations of unetched and etched layers reveal particle-like defects of micron size, stacking faults, dislocations, and saucer pits. TEM shows interfacial defects of tens of Angstroms size at the substrate-epitaxial layer interface. Reproducible defect densities are given for various in-situ cleaning procedures.

High energy ion scattering/channeling and low energy electron diffraction are usedfor an investigation of the initial stages of interface formation during Si homoepitaxy. We find a strong dependence of the atomic. reordering – a necessary condition for pseudomorphic growth – on substrate surface, deposition temperature and Si coverage: (1) Si deposition at 300 K reorders the Si(100) substrate reconstruction in a layer by layer manner. In contrast Si( 111) is unaffected by Si deposition at that temperature. This difference between Si(100) and Si( 111) can be understood in terms of different structural models. (2) On both surfaces deposition at 300 K results in a disordered overlayer. (3) As a direct consequence of the dependence of the reordering on reconstruction we find a lower epitaxial temperature (≈570 K) for Si(100) than for Si(l 11) (≈790 K).

Using a specially modified ultra-high vacuum, ultra-high resolution transmission electron microscope, in-situ cleaned Si surfaces have been examined with near atomic resolution. By annealing the edges of a <110> thin Si specimen in-situ, it is found that low energy surfaces form. A surprising observation is that the {113} surface is stable and reconstructed by dimerization to a very low dangling bond density. It is also found that a 7×7 surface peridoicity can be preserved at a buried Si < 111 > / amorphous Si interface.

Extremely high controllability of the carrier concentration of p--InP below 1×l0l6 cm−3 has been obtained by using Mn as a dopant. Applying Mndoped p--InP to the current confining layers of 1.3 µm buried heterostructure (BH) laser diodes has enabled threshold currents as low as 12 mA.

Surface morphologies of the molecular beam epitaxy (MBE)-grown GaAs layers using the background-arsenic-pressure-control method were investigated. The growth parameters, such as substrate temperature, growth rate, epilayer thickness, As/Ga ratio, doping concentration, substrate type, etc., are related to the observed oval defect density. Protrusions and Ga-droplets caused oval defects during growth. The origin of the oval defects in our system is found to be the gallium oxide, not Ga "spitting" from the effusion cell.

The growth of epitaxial GaAs layers on semi-insulating substrates, using high purity GaAs as source material has been obtained by the so-called lose Space Vapor Transport technique. The thermodynamical conditions of the growth, the effect of the growth parameters : source and substrate temperatures, pressure of transporting gas (water vapor) on the growth rate were investigated. Then, the variations of the optical, electrical and deep levels properties of the layers were studied as a function of the growth parameters in order to determine the values of these parameters for which the layers present the best electronic properties. Here, we describe i) the evolution of the photoluminescence spectra versus the substrate and source temperatures, the water vapor pressure being kept constant at its best value; ii) a secondary ion mass spectroscopy analysis of the main impurities contained in the layers. The results demonstrate that the layers are homogeneously Si and S doped, the doping being slightly compensated, the layer-substrate interface is clean and the PL is characteristic of a defect free material.

Heavily Si-doped aluminium arsenide films on GaAs substrate by MBE have been investigated. It is found that the Si activation energy ED for AlAs films decreases with increasing Si donor concentration, approaching a few meV for n≧3×l018. The maximum free electron concentration of n=7×l018 cm−3 and electron mobility of 200 cm2/V.sec for n=5×l017 were obtained. It is also shown that the replacement of the ternary AlxGal−xAs with a superlattice having heavily Si-doped binary AlAs in the barrier layers is effective to increase free carrier concentration.

Solid phase epitaxial growth of electron beam evaporated Ge layers on unheated GaAs has been demonstrated. The amorphous Ge layers grow epitaxially on the GaAs surface during anneals at 400°C. A technique for growing these epitaxial layers without the need for in-situ heat treatment of the GaAs prior to Ge deposition is described.

The growth of polar semiconducting materials on non-polar semiconducting substrates is illustrated by experimental observations of GaAs grown on Ge substrates and on Ge epilayers which had been grown on Si substrates. The GaAs epilayers are grown in each case by metal-organic, vapor-phase deposition. The GaAs/Ge heterophase junction, the grain boundaries in GaAs grown on {110} Ge and on {001} Ge/Si composit substrates and the anti-phase boundaries in GaAs grown on {001} Ge substrates are eat.h illustated. The interfaces have been studied by transmission electron microscopy and reveal the pronounced faceting of the anti-phase boundaries in GaAs. Also demonstrated experimentally is the strong interaction between dislocations/grain boundaries and these anti-phase boundaries.

High-quality single domain GaAs epitaxial layers were successfully grown on (100)Ge substrates. Growth was carried out using conventional metalorganic chemical vapor deposition at atmospheric pressure. Antiphase domain free GaAs epitaxial layers were obtained by thermal etching of the Ge surface just prior to growth. Mosaic surface morphology and antiphase boundaries characteristic of domain structures were completely absent in epi-layers following thermal etching. Photoluminescence revealed that domain free epi-layers exhibited characteristics comparable to those of GaAs homoepitaxial layers.

CdTe evaporates into Cd and Te atoms under high power, pulsed laser irradiation. The mechanism is different from thermal evaporation where only atomic Cd and molecular Te are formed. The presence of Te atoms is responsible for some unique nucleation processes, such as the epitaxial growth of CdTe on (111) CdTe substrates with either polarity and the enhancement in sticking coefficient in CdTe deposition.

Two epitaxial orientations [(111) and (100)] of CdTe are grown on (100) GaAs in the presence of a 14.6% lattice mismatch. Consistent nucleation of a selected orientation is achieved by employing specific growth techniques. The growth techniques for selection of both orientations are described. High resolution electron microscopy has been used to investigate the interface between the CdTe epilayer and the GaAs substrate. For the (111) orientation strong interaction exists between the epitaxial deposit and the substrate, whereas a weakened interaction between deposit and substrate induces the (100) orientation.

A series of MBE grown CdTe films were grown on (100) InSb substrates. The substrate temperature, Ts, was varied from 170° to 285°C in eleven steps. Low temperature (∿2K) photoluminescence measurements and TEM have been combined to show a strong correlation between defect density and the details of the luminescence spectra. A natural division is obtained for samples grown with substrate temperatures from 285°C to 250°C (Region I) and from 225°C to 170°C (Region II).

Hgl−xCdxTe layers have been grown on CdTe substrates using dimethylcadmium, diethyltelluride and mercury in a horizontal reactor. Details of conditions for growth of these layers are presented in this paper. Specular surfaces of Hg1−x CdxTe with × ≥ 0.15 were obtained on (100) 3°, → (110) oriented CdTe substrates. Both n-type and p-type layers could be obtained. The mobility of these layers was measured over the temperature range of 10 K to 300 K. The mobility of n-type Hg.81 Cd.19Te layers, measured at 2.1 kG, was 3.0 × 105 cm2/V-sec at 60 K, falling to 2 × 105 cm2/V-sec at 10 K. P-type layers were also grown, and are described in this paper.

An etch pit study has been made on misfit dislocations in (111) HgCdTe-CdZnTe heterojunctions grown by liquid phase epitaxy. It was shown that misfit dislocations were localized at the original surface of the substrate, because Zn diffused into the epilayer during epitaxial growth prevents movement of dislocations. For lattice matching between Hg0 7Cd0.3Te and Cd1−yZnyTe, the optimum ZnTe mole fraction of Cd1−yZnyTe was found to be 2.9%.

X-ray double crystal diffractometry provides a means of rapidly characterizing epitaxial structures. Because the technique is rapid and nondestructive and because it yields a wealth of information, rocking curves have been routinely obtained and extensively studied by us. We present here selective results illustrating the typical progression in layer quality which occurs from the initial growth in a reactor to the growth of device quality material.

The technique is described for use of x-ray double crystal diffractometry for analysis of epitaxial structures. This method has been shown to be very useful for characterizing a wide variety of configurations, ranging from single epitaxial layers to damaged superlattices. It yields depth profiles of structure factors and strains relative to the substrate, which can be directly related to layer thicknesses and compositions. Information about dislocations and random atomic displacements is also present. The key to this technique is computer fitting of the x-ray data with a model for the diffraction process, utilizing trial profiles for the strain and structure factors of the epitaxial layers. In the work to be presented a kinematic model for the diffraction is used. The technique is demonstrated with analyses of an Alx Ga(1−x) As single layer on GaAs, an AlSb/GaSb superlattice on GaSb, epitaxial CoSi2 on Si, and ion-implanted and annealed AlxGa(1−x)As superlattices on GaAs.