From a comparative study using scanning tunneling microscopy, high-resolution lowenergy electron diffraction, and reflectance difference spectroscopy, we investigate the optical anisotropy on clean and H-covered Si(001) surfaces. We demonstrate a high sensitivity of reflectance difference spectroscopy to the surface tructural anisotropy and surface chemistry.

The photoluminescence and Raman scattering of {|(CdSe)1 (ZnSe)3|14-(ZnSe)130} × 5 multiple quantum well structure have been investigated at 77 K and under hydrostatic pressure up to 7 GPa. Resonant excitations have been accomplished by turning the electronic levels under hydrostatic high pressure. Two kind of excitons and ZnSe-like LO phonon modes as well as their pressure behavior are presented.

This paper reports on the study of the gettering of nickel contamination in hydrogen annealed CZ-silicon wafers by using method of wet chemical analysis. According to the wet chemical analysis, we believe that the hydrogen annealed wafer is of high quality in the region beneath the surface (DZ) and has a higher gettering ability for nickel compared with conventional CZ wafers. This observation is also in agreement with our MOS C-t measurements.

The resistivity and interfacial characteristics of Pd/Zn/Pd/Au and Pd/Zn/Au/LaBd6/Au contacts to p-In0.53Ga0.47As have been investigated. Annealing of the contacts at 375–425°C yielded a minimum in specific contact resistance, p,, of 2 × 10-7 Δ cm2 for the Pd/Zn/Pd/Au contacts and 1 Δ cm2 for the Pd/Zn/Au/LaB6/Au configuration. This is the lowest reported measurement of pc for an ohmic contact to p-In0.53Ga0.47As doped to ≤1 × 1019 cm−3. In the Pd/Zn/Au/LaB6/Au scheme, the minimum in pc was the same irrespective of whether the Zn was incorporated as a structural layer or as Zn ions implanted into the interfacial Pd prior to metallization. The effect of thickness of the Zn layer on pc has been determined for the Pd/Zn/Au/LaB6/Au scheme. RBS measurements have shown that during annealing, the LaB6 layer acted as a barrier to the indiffusion of Au and to the degradation of the In0.53Ga0.47As substrate.

Extreme variations in surface reflectivity/topography have been observed on silicon wafers with evaporated aluminum metallization following thermal annealing processes. Such topographic variations negatively impacted the performance of wire bonder pattern recognition systems. It was proposed that this variation was attributed to differences in deposition rates during evaporation of the aluminum front metallization. SEM analysis revealed that the topographically rough sites, deemed as normal for this processing sequence, had large numbers of hillocks, while the smooth sites exhibited limited numbers of hillocks after heat treatment. SIMS depth profiling analyses did not indicate that any elemental difference existed between the smooth and the rough sites, although interfacial differences were detected. Specifically, the Al-Si interface for the rough surface was more graded in nature while the Al-Si interface for the smooth surface was more abrupt. TEM analysis of the rough sites revealed that a three-dimensional island growth mechanism prevailed during film growth, resulting in uneven surface development, whereas analysis of the smooth sites showed a columnar grain structure.

Ohmic contact has been observed to play an important role in the performances ofLiquid Encapsulated Czochralski gallium arsenide particle detectors since it is possible to control the injection of charge carriers which determines the device performances. Alloyed and implanted contacts characteristics have been compared to relate the presence of electrically active defects induced during contact preparation to the final detector efficiency. In-situ optical probing investigations have been carried out to analyze the electric field distribution. Spectroscopic investigations show that the contact fabrication process significantly influences the trap density, whilst it does not change their type.

In recent years the use of non-destructive techniques involving the generation of minority carriers by means of an electron beam (EBIC) or a LASER beam (OBIC) have proven to be useful in the study of the electrical properties of process-induced defects in bulk silicon. The development of a model and algorithm to obtain the diffusion length L, the surface recombination ratio S and the defect-increased recombination, by collecting the LASER-Beam-Induced-Current scanning the sample using a Schottky diode is presented. First a model to obtain the probability of collection of an electron-hole-pair generated by a point source is derived. The finite size of the collecting junction, L and S make the solution of the diffusion equation available only in integral form; it is therefore necessary to perform a numerical integration. Then a least-squares algorithm for identifying L and S in the case of bulk silicon without defects is obtained. Lastly the effect of a finite size generation volume and the increased recombination due to a line defect is taken into account. The effect of S and the distance of the defect from the surface on the signal contrast is analysed. This determines the information depth of the collected signal. It is shown how a high value of surface recombination ratio reduces the contrast and therefore impairs the possibility of detecting low-strength defects.

An analysis of the experimental results is performed and they are found to be in good agreement with the model.

Photoluminescence (PL) and Hall measurements allow one to obtain important parameters of semiconductors, such as impurity concentrations, compensation, and activation energies (EA). Usual analyses of such data assume constant EA. However, it is well known that EA depends on free carrier and impurity concentrations, and thus on temperature, due to screening effects. We here analyze literature data on ZnSe:N using screening effects. An observed decrease of EA with temperature (from PL data) had been used to suggest an interstitial site for N. With inclusion of screening, we obtained good agreement with the data, so that the idea of interstitial N is not required. In applying the screening theory to Hall measurements, we obtained lower impurity concentrations than with use of a constant EA. It is also to be noted that we fit both optical and electrical data with this approach. We further suggest that screening is the cause of an observed difference between optically observed and thermal activation energies.

Acoustic emission (AE), electric current fluctuation, as well as luminescence intensity fluctuations in lightemitting semiconductor structures have been investigated. The authors examined the hypothesis about the origin of nonelectronic acoustic low frequency noise that is observed in electronic systems. The various sets of AE's sources allow one to understand the various dynamics of the AE in the structures on the A3B5 compound base and p-n germanium diodes.

We have studied GaAs/AlAs periodic quantum dot arrays using high resolution x-ray diffraction (reciprocal space mapping) around the (004) and (113) reciprocal lattice points. From the distribution of the diffracted intensities we deduced the average strain status of the dots. From the numerical simulations it is evident that random elastic strain fields are present, which extend through almost the entire volume of the quantum dot. The simulations of the x-ray measurements revealed that the crystalline part of the dots is considerably smaller as scanning electron micrographs would indicate.

It is shown that an x-ray interference phenomenon, Coherent Grating X-ray Diffraction (CGXD), can be used to study lateral nanostructure arrays on crystal surfaces and interfaces. Compared to Fraunhofer grating diffraction of visible light, x-ray grating diffraction contains information not only about geometric profiles of a surface, but also about the internal crystalline structures and lattice strain distributions in grating features. Grating diffraction patterns can also be measured in a white-beam Laue method using highly collimated polychromatic synchrotron radiation. This provides a way for parallel data collection and is useful in in-situ studies of structural evolution of nanostructure arrays.

An overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.

We describe a technique for measuring thin film stress using wafer curvature that is robust, compact, easy to setup, and sufficiently sensitive to serve as a routine diagnostic of semiconductor epilayer strain in real time during MBE or CVD growth. We demonstrate, using growth of SiGe alloys on Si, that the critical thickness for misfit dislocation can clearly be resolved, and that the subsequent strain relaxation kinetics during growth or post-growth annealing are readily obtained.

Bulk GaAsP, 20Å–500Å GaAsP/GaInP single quantum wells and 70 Å period GaAsP/GaInP superlattices were deposited on GaAs substrates by Flow Modulation Epitaxy. In these structures, the disordered GaInP is lattice matched while the GaAsP is in tension with the As mole fraction varying from 0.6 to 1. The structures were studied using asymmetric x-ray diffraction, 1K photoluminescence, Raman scattering, transmission electron microscopy and atomic force microscopy. Raman and x-ray diffraction are used to assess the structural quality of the superlattices, especially with regard to the presence/absence of superlattice x-ray satellites and disorder activated longitudinal acoustic phonons. A model including the effects of composition, strain, and confinement on longitudinal optic phonons is described and used to estimate the composition, using Raman scattering, in the thin, pseudomorphic GaAsP layers in the superlattices. Photoluminescence is used to assess the composition of the interfacial layers in the single quantum wells and to determine transition energies in the superlattices. In addition, analysis of the heterostructure luminescence, including prediction of the energy band alignment as calculated with the model solid theory corrected for strain, is found to suggest the presence of a type II band alignment in the heterostructures for some values of GaAsP composition. Finally, Raman scattering and x-ray diffraction are used to compare arsenide to phosphide interfaces in GaAs and InP-based heterostructures.

A novel method for determining thin film density by energy dispersive x-ray reflectivity is demonstrated for a polymer-derived spin-on-glass dielectric intended for microelectronics applications. The effects of sample misalignment limit the accuracy of x-ray reflectivity as typically practiced. These effects may be properly accounted for by measuring the critical angle for reflection at many different x-ray wavelengths simultaneously. From this measurement, thin film density can be ascertained with much improved accuracy. The results of the x-ray reflectivity measurement are compared to those derived from MeV ion scattering.

X-ray absorption spectroscopy has been applied to layered Zn-doped InP structures containing systematically varying amounts of Zn spanning a factor of -40. The structures, similar to those used in optoelectronic laser devices, were characterized with x-ray absorption spectroscopy and SIMS to determine quantitatively the Zn concentrations. In addition to being non-destructive, the former technique was shown to be substantially more precise. A well-defined concentration regime is established in which substitutionally occupied Zn is directly proportional to Zn exposure during growth.

Spectroscopic Ellipsometry (SE) and Grazing X-ray Reflectance (GXR) techniques are applied on different III-V epitaxial structures in order to extract accurately their structural information. Thickness information are obtained directly from Fourier transformation of the GXR spectra and confirmed by simulation of the reflectance curve. Compositions are deduced from SE regression using GXR thickness as input values. Examples on monolayer and bilayer structures are first remembered. Then the potentiality of the method is demonstrated to more complex systems (multilayer mirrors and HEMT structures).

We have achieved spatially resolved room temperature photoluminescence (PL) from MOVPE GaAs (001) surfaces by Near-Field Scanning Optical Microscopy (NSOM). The PL intensity variation was related to the change of surface state density. Using this technique, the uniformity of surface passivation after (NH 4)2S treatment has been studied. We have performed the topography, reflection and PL measurements by NSOM as well as the topography measurements by Atomic Force Microscopy (AFM) on the as grown, etched and sulfur passivated GaAs samples. The uniformity of GaAs with a thin Al0.65Ga0.35As cap layer has also been studied and compared with the (NH 4)2S treatment. We found the sub-micron scale variations in PL intensity which were not correlated to the topographic features. Theoretical modeling has been used to obtain semi-quantitative analysis of the experimental results.

A new GaAs surface passivation method, CS2 treatment at moderate temperature was developed for effective passivation of GaAs surfaces. The CS2 treatment of GaAs surfaces at 350°C and 10 atm leads to deposition of a homogeneous film, with a thickness of several hundred Å. The passivation layer thus produced causes a significant enhancement in room temperature photoluminescence intensity and the passivation effect of the sulfide film was confirmed by Raman spectroscopy. The passivation layer remained electrically and chemically stable over a period of nine months under ambient atmospheric conditions. In-depth Auger electron spectroscopy (AES) revealed that the carbon and oxygen content in the film was negligible, whereas sulfur was uniformly distributed throughout the film. A metal-insulator-semiconductor diode whose insulating layer is produced by the CS2 treatment shows well-defined accumulation and depletion regions in its capacitance-voltage (CV) characteristics with low hysteresis.

Cathodoluminescence (CL) technique has been employed to study the optical properties of GaSb after deposition of hydrogenated amorphous silicon (a-Si:H). CL images recorded at various depths in the samples clearly show passivation of extended defects on the surface as well as in the bulk region. The passivation of various recombination centres in the bulk is attributed to formation of hydrogen-impurity complexes by diffusion of hydrogen ions from the plasma. Enhancement in luminescence intensity is seen due to passivation of non-radiative recombination centres. The passivation efficiency is found to improve with increase in a-Si:H deposition temperature.