The physical nature of the InP near-surface defect acceptor and donor states are studied by using photoemission spectroscopy. It is found that the In/n-InP(110) interface band bending does not start until the In coverage reaches about 0.3 monolayer (ML), while the In/p-InP(110) band bending is almost saturated at 0.3 ML. The annealing effect on the band bending of clean cleaved n-and p-type InP(llO) surfaces is also studied. It is found that annealing of the clean surface creates an irreversible band bending effect on the p-InP(110), but the n-InP(110) almost does not show any band bending after low temperature annealing. Based on these two striking differences in the band bending behavior of n- and p-type InP, it is proposed that the physical nature of InP near-surface defect acceptor and donor levels may be different and that phosphorus vacancies are the cause of p-InP surface Fermi level pinning.

The luminescence properties of MBE-grown pseudomorphic InxGa1−xAs—GaAs quantum-well structures are examined as a function of photoexcitation intensity and temperature. The structures examined consist of single In0.28Ga0.72As or (isolated) multiple In0.16Ga0.84As pseudomorphic wells sandwiched between thick, unstrained GaAs confining layers. Low-temperature photoluminescence spectra for these samples, which range in quantum-well thickness from 17 Å to 50 Å, consist of a single feature attributable to transitions associated with n = 1 electron and j = 3/2, Mj = 3/2 > - hole states. Spectral widths of these peaks are very narrow (7–11 meV), even for a heavily spike-doped sample (Si, ND ∼ 1018 spike-doped at well center). Emission intensities for the quantum-well structures are studied as a function of excitation intensity over the range 3 × 102 ≤ Pex ≤ 6 x 1O4 W/cm2, and one of the samples (x = 0.16, 50 Å undoped wells) prepared as a laser structure is shown to support stimulated emission at an excitation intensity < 104 W/cm2. The excellent luminescence properties of these structures are shown to degrade rapidly with increasing temperature, with radiative efficiencies dropping more than two orders of magnitude over the temperature range 20K – 180K. One possible explanation for this behavior is proposed.

Two 2-dimensional electron gas (DEG) regions coupled either by a superlattice, an undoped GaAs layer, or the combination of a tunneling barrier with a superlattice have been investigated by studying (a) non-ohmic conduction, (b) field effect characteristics parallel to the 2DEG channels and (c) negative differential resistance (NDR) for conduction perpendicular to the quantum wells. It is shown that coupling is optimized when the separation region is a superlattice. Tunneling through superlattice mini-bands can enhance field effect transistor transconductance.

Monte Carlo based microscopic techniques were used to study the stability and metastability of thin coherently strained layers of mismatched siliconlike semiconductor material grown on the (111) silicon surface. The structural energy was calculated using three-body empirical potentials. For layers greater than about 20 Å thickness, the critical layer thickness associated with thermodynamic stability agrees quantitatively with continuum theory. For thinner layers, however, considerable variations from the continuum theory are found. For a strained layer six monolayers thick, the test system is found to be metastable against the nucleation of misfit dislocations to a lattice mismatch of about 11%, compared to the 4% equilibrium stability limit.

We define the Interface between two dissimilar materials by two functions, g(z) and f(x,y), representing the diffuseness along the interface normal and the distribution of interface non-planarities respectively. We show how these functions may be measured for the case of epitaxial interfaces between dissimilar crystals by quantitative analysis of lattice structure images obtained by high resolution transmission electron microscopy. Experimental examples are drawn from the GeSi/Si, InGaAs/InAlAs and InGaAs/InP systems. Correlations between interface structure and optical and electronic properties of these systems are discussed.

Multiple peaks, recently observed in the low temperature photoluminescence (PL) spectra of GaAs/AlGaAs single quantum wells fabricated by momentarily interrupting the molecular beam epitaxial growth between adjacent but different semiconductor layers, have been interpreted as originating within smooth regions in the quantum well layer differing in width by exactly one monolayer. We have observed similar structure in similarly grown samples but find that low temperature PL can be misleading. However, higher temperature PL or PL excitation spectroscopy do provide unambiguous evidence for the model of interface smoothing due to growth interruption. Further, time-resolved spectra yield decay times of the individual peaks which are consistent with this idea.

Low-temperature magneto-luminescence studies are used to examine the in-plane valence-band dispersion in GaAs/GaPAs strained-layer-superlattice structures. The results provide a direct observation of valence-band mixing effects in strained-layer systems.

Theoretical and experimental studies of the effect of valence-band mixing upon the magneto-transport properties and magneto-luminescence data for GaAs/AlGaAs latticed-matched superlattices have been recently reported.[1–] Due to the presence of the 2D-quantum well, the valence-band degeneracy between the light-hole and heavy-hole bands at is removed. These studies show, however, that the lowest energy valence-band mass is still strongly dependent upon due to valence-band mixing. On the other hand, because of the large biaxial compression in strained-layer-super lattices (SLS), valence-band mixing effects should be minimal.[8–9] Recent magneto-transport measurements[10] on p-type InGaAs/GaAs SLS structures have provided information regarding nonparabolic valence-bands in these structures.

The use of a cleaved 90 degree wedge as a cross section sample for transmission electron microscopy allows the composition of III/V semiconductor alloys to be measured by studying the thickness fringes of the on-axis [010] bright field image. The effect is explained in terms of the incident electron Bloch states and is illustrated by reference to GaAs/AlGaAs. The technique has an accuracy of about 5% and a spatial resolution of a few Å. The range of materials that can be analysed in this way is discussed.

The measurement of Shubnikov-de Haas(SdH) oscillation is proposed as a new technique for evaluating the quality of a heterointerface. The first excited state of 2-dimensional electron energy levels is determined for several samples using the measurements of SdH oscillation. Lower values of the first excited state energy are found for the samples with a low mobility. The low value can be approximately explained in terms of graded interface model.

The deposition of gold film onto aluminum alloy substrate was attempted by the Ionized Cluster Beam(ICB) deposition process. The adhesive strength, reflectivity, and geometrical accuracy(conformance to specifications) were evaluated for the films deposited under various acceleration voltages and substrate temperatures. The film-substrate interface was examined by Auger electron spectroscopy and x-ray diffraction. A gold film with reflectivity of 99.2 % and an adhesive strength of over 4–0 N/mm2 was obtained by ICB deposition at room temperature. It was established that a high adhesive strength can be achieved by ICB deposition even if a surface oxide layer on the substrate remains.

The structure of copper-hafnium multilayers has been studied as a function of composition modulation wavelength by x-ray diffraction and EXAFS. Sputter deposited samples were produced with composition modulation wavelengths of 1/2, 5, 7, 10, 14, and 20 close packed planes of each constituent per layer. The structure evolved anisotropically from amorphous to crystalline with increasing composition modulation wavelength, with crystalline order first appearing in the growth direction in the 7 mono-layer sample. Structural coherence in the growth direction was not observed to extend beyond one elemental layer in any sample, and evidence for a disordered interfacial layer was observed by EXAFS for all samples. Small angle x-ray diffraction showed strong composition modulation for all but the 1/2 monolayer sample. The amorphous interface is the result of reaction during deposition similar to the solid state reaction observed in other systems such as nickel-zirconium.

The perfection of epitaxial nickel films grown on the (00.ℓ) or basal plane of heated sapphire (A1203) single crystals were studied with X-ray diffraction techniques. Nickel films approximately 700 Å thick formed by vapor deposition increased in perfection as the temperature of the sapphire approached 1400°C. Although the nickel atom distances are 10.3% smaller than those of the closed-packed direction in sapphire, the strain was accommodated at the interface rather than being distributed through the thickness of the nickel film. Diffuse rods of X-ray scattering which are associated with diffraction from the interface gave information about the nature of the roughness at the interface.

The binary alloy series of Ti-X metallic, composition modulated layered structures has been fabricated via magnetron sputtering. The Ti-X systems (where X is Ta, Mo, or V) explored are exemplary of solid solution systems, such as the supermodulus systems of Cu-Ni, Ag-Pd, Au-Ni, and Cu-Pd (which all feature fee crystalline compatibility). In the present case, the beta-phase of Ti sought in these Ti-X systems suggests bec crystalline compatibility, with interlayer misfit strains not exceeding 10%.

The Ti-X series examined, matches elements of high and low atomic number. (Z of Ti, V, Mo, and Ta are 22, 23, 42, and 73, respectively.) Difficulties which arise in a conventional tungsten basket - alumina crucible physical vapor deposition process, i.e. obtaining thr vaporization temperatures for Ti, V, Mo and Ta of 1235, 1332, 1822, and 2240 °C at 130 mPa, respectively, are overcome by magnetron sputtering. Thin films produced by alternate deposition of Ti with V, Mo, or Ta, are desired with individually unique, regular repeating layer thicknesses which range from 1.5 to 15 nm.

An initial characterization of the Ti-X composition modulated alloys has been conducted using X-ray diffraction. The pole figure constructions of the various composition wavelengths give a qualitative look at the strain accomodation within the thin films and possible manifestations in mechanical properties.

We have studied the superconducting properties of V/Cr superlattices. Superlattices of V100Crx, V150Crx, and V200Crx, with x varying between 3 and 80 atomic planes have been prepared. The films have a strong (110) texture and were grown on sapphire substrates at 250°C in an ultra-high vacuum system. The zero field transition temperature of the V150Crx and V200Crx, but not the V100Crx films have been adequately modeled using Werthamer's theory for proximity effect coupled films. The films have a dimensional crossover in the parallel upper critical field when the thickness of the Cr layers is about 60 atomic planes.

Several series of multilayered Fe/Cr films have been studied, each with a fixed thickness of Fe and several thicknesses of Cr. The coer-civity and in plane anisotropy field were found to increase abruptly for larger Cr thicknesses. The origin of this change in behavior may involve a paramagnetic/antiferromagnetic transition in the Cr.

In a number of vapor deposited aluminium alloys grain growth has been investigated systematically by means of quantitative electron microscopy and found to proceed not by grain boundary migration, but by grain coalescence. Parameters influencing the observed mode of grain growth will be discussed with respect to the formation of microstructures with optimal resistance to electromigration, i.e. microstructures with large grain size, high homogeneity in the grain size distribution as well as a strong texture.

Analyses of grain size distribution after annealing indicate a strong retardation in grain growth by the solute in all aluminium alloys except Al(Cu). Relative large grain sizes and very small lognormal standard deviations have been observed in Al-l%Cu as well as ternary Al(Cu,Hf) thin films.

Many metallic superlattices are known to exhibit dramatic anomalous elastic properties as a function of modulation wavelength. All measurements to date measure either a shear modulus or a longitudinal modulus in the superlattice plane. Here we present a method which also probes longitudinal elastic behavior perpendicular to the layers using a nano-hardness tester. In this method, a diamond tip is indented into the material and both the indentation depth and applied force are constantly monitored during loading and unloading. The elastic properties are extracted from the unloading part of the force versus displacement curve. Contrary to the anomaly found in a shear modulus, no anomaly in Young's modulus was found in the present study on Mo/Ni superlattices.

The metallurgical reaction at 450°C in forming gas ambient between the Ti diffusion barrier and Al, causing the contact degradation in the Al (1% Si)-Ti multilayer interconnects has been studied. The Ti-Al reaction is reduced by preheating the Ti layer in N2 using rapid thermal processing (RTP) at 2.500°C. The curtailed reaction is attributed to the thin surface titanium oxynitride layer. It was found that a 1000-Å Ti layer inserted between the multilayer and Si is effective as a sacrificial diffusion barrier against contact degradation, but 500-Å Ti is not. RTP of the thin Ti film rendered it effective as a diffusion barrier.

TEM, X-ray diffraction, and electrical resistivity measurements were used to study the microstructure and the growth of AI-Cr-AI film sandwiches, where the individual Al layers were 300 Å thick and the Cr thickness was varied between 0–10 atomic layers. The base vacuum was around 1.0 × 10−10 torr, substrate temperatures varied between 100–350 °C, and evaporation rates were 3Å/s for Al and ∼0.1 – 0.2 Å/s for Cr. All Al films had a strong (111) texture and showed a non-percolative island structure at 350 °C. The films became connected at lower substrate temperatures, reaching perfect continuity at 100°C. However, electrical conductivity is achieved also for the films deposited at 350 °C when one or more atomic layers of Cr are sandwiched between the Al layers. Results for the superconducting critical temperature and resistivity are discussed in terms of Cr diffusion into Al and the film size effect.

We report theoretical calculations of deep levels in GaAs/AlxGa1−xAs superlattices under hydrostatic pressure. We predict phase diagrams for DX centers: for a given composition x there is a function p(a), which relates pressure p and GaAs quantum-well width a, and defines a phase boundary between two regions: one in which DX is a deep trap in the fundamental band gap and another in which the DX deep level lies in the conduction band.