We have measured systematically low-temperature photoluminescence spectra associated with deep acceptors due to 3d transition metals in GaAs bulk crystals in order to get some basic knowledge necessary for the characterization of these deep acceptors and related impurities or defects in GaAs. A series of the 3d transition metals, Cr, Mn, Fe, Ni and Cu, in GaAs have been studied, the luminescence spectra showing some characteristic emission lines for each transition metal in the near-infrared region. These results provide a spectroscopic characterization method for the identification of these impurities in GaAs. Analysis of the luminescence data indicates the formation of various complexes including a transition metal with another defect or shallow impurity. The in-depth profiles of these deep center luminescence intensities have been measured for the cases of Cr and Ni, the results indicating the usefulness of the photoluminescence technique for the characterization of the in-depth profiles of shallow impurities and defects such as an arsenic vacancy. In particular, the in-depth profile of the Cr-related luminescence line in annealed GaAs:Cr has been studied to investigate the distribution of such defects in GaAs crystals.

The effect of CW argon laser radiation on a GaAs-AlAs multiple quantum well structure was studied. Raman scattering and quantum well lumiunescence excited by the same laser beam were used as probes. It was found that most important changes in the spectra were caused by laser beam heating of the crystalline lattice. The temperature inside the laser beam was determined as a function of laser power, position in the laser spot and scanning speed. An irreversible transformation of the superlattice to a phase with different optical properties was observed at a laser power threshold of 24kW/cm2; this is much lower than the threshold for sample destruction. Temperature dependences of energies of quantum well transitions and LO GaAs-like phonons were also measured. Breit-Wigner-Fano interference between LO AlAs-like phonons and the Raman active continuum was found.

The results of an investigation of optically pumped double-heterostructure lasers are reported. Threshold power densities of ≈8-35 kW cm-2 and a total power efficiency of ≈10% have been measured. Gain spectra have been derived from the data for several pumping configurations. Photogenerated carrier concentrations have also been calculated from the spectra. Current injection devices have been fabricated to assess the utility of this method for predicting lasing wavelengths and threshold current densities.

We review a number of recent significant developments in the use of Raman scattering (first-order as well as second-order) to characterize semiconductors in bulk, thin film or device form. Areas to be discussed include microcrystalline and amorphous tetrahedrally bonded solids (particularly Si), ion-damage and laser-annealing effects, microscopic nature of potential fluctuations in alloy semiconductors (including single crystal metastable materials), determination of the composition dependence of conduction band effective mass and scattering times, HgCdTe and CdTe, zone-folding in superlattices, correlation of light scattering and transport properties in quantum well structures, interfaces (including semiconductor/vacuum, Schottky barriers, MOS, heterojunctions) and determination of strains (including temperature dependence) at the interface of Si on various substrates.

By measuring the Raman frequency shift due to a two-dimensional stress induced in silicon thin films in various substrates having thermal expansion coefficients above and below that of silicon, we have characterize the strength of bond between the silicon film and the substrate. Therefore our approach offers a quantitative measure of microadhesion.

Raman scattering and photoluminescence spectroscopy in the presence of high magnetic fields (0-19 Tesla) have proved to be sensitive and fruitful techniques for investigating the behaviour of two dimensional (2D) electrons in multiquantum well (MQW) heterostructures. A systematic study of MQW GaAs-AlxGa1-xAs samples, grown by MBE and modulation doped with Si to give electron areal densities in the range of 2-7x10" cm-2 has been undertaken. Two kinds of field dependent excitations are observed in the Raman spectra that are characteristic of clean, well defined 2D layers. One corresponds to transitions between Landau levels (cyclotron resonance); the other is a collective magneto-plasma mode.The effect of magnetic field on the luminescence spectra from the recombination of 2D electrons with photo injected holes is marked at fields as low as 2 Tesla. The electron continuum breaks in Landau levels related to electron exchange energy and competition for dominance in the valence band between confinement and magnetic field effects. At higher fields, the peak luminescence efficiencies increase with a concomitant decrease in the individual line widths. Discrete slope changes are observed and the lowest Landau transitions split into circularly polarized doublets. The magnetic field dependent luminescence spectra in the Si modulation doped MQW heterostructures is manifestly different from the behavior of free excitons and electronic transitions associated with ionized donor, acceptor or neutral impurities. Consequently both magneto-Raman and -photoluminescence techniques offer a non-destruc-tive method of characterizing these materials.

In this paper, I review the use of spectroscopic ellipsometry (SE) to determine properties of bulk materials, thin films, and interfaces. The relationship of SE to other characterization techniques and the role of optical modeling in representing average or effective properties of microstructurally complicated structures is discussed. The present state of instrumentation is described and prospects for future developments are indicated. Recent progress in data reduction and analysis includes the development of Fourier methods to minimize noise and baseline effects and to improve accuracy in data manipulation and the determination of critical point parameters, and of systematic methods to determine thicknesses of films for which the dielectric properties are unknown. Examples included illustrate the determination of bulk density and alloy composition, microscopic roughness, constituent fractions of heterogeneous materials, dielectric properties of overlayers, and the properties of buried interfaces. A list of references to other work and to more detailed treatments of the topics discussed here is given at the end.

A number of properties of semiconductor silicon during the various stages of the device manufacturing can be measured by Fourier transform infrared spectroscopy. In this paper, the accurate determination of the interstitial oxygen concentrations including the corrections for the effect of multiple reflections in the silicon wafer will be described. Microscopic mapping of the oxygen distribution from sampling areas of 25 micrometers or less in diameter will also be described. Methods are also outlined for the accurate determination of the phosphorus and boron concentrations in phosphosilicate, borosilicate, and borophosphosilicate glasses on silicon.

Fourier methods allow the separation of baseline, information, and noise in reciprocal space, thereby permitting more accurate derivative lineshapes to be calculated, more accurate interpolations and Kramers-Kronig transformations to be performed, and more accurate estimates to be made of the critical point parameters that describe structure in optical spectra. These techniques are discussed and applied to ellipsometrically measured pseudodielectric function spectra of the semiconductor alloy sequences AlxGal-xAs and GaAs1-xPx. The x dependence of the El and El + Δl critical point energies of AlxGa1-xAs shows definite departures from quadratic behavior. In the E0 - E2 spectral region significant level crossings are observed for AlxGa1-xAs, while the corresponding structures for GaAs1-xPx shift uniformly with x.

This paper presents a review of techniques for spectroscopic characterization of mile gas pnase species involved in vapor depositon and plasma etching, two processes of great importance in the semiconductor industry. Descriptions of the apparatus requirements and capabilities of diode laser absorption and dye laser resonance fluorescence detection techniques are given. In addition, band strength and other spectroscopic data for selected molecules are used to give estimates of the detection sensitivity for various species.

We have studied transitions from shallow core levels to lower conduction band states in In1-xGaxAsyP1-y, In1-xGaxAs, and In1-xGaxSb using synchrotron radiation reflectance spectroscopy in the 17.5-21.5 eV photon energy range. Fits of third derivative lineshapes yield core-conduction energies modified by excitonic effects. The nonlinear variation of these energies is mostly determined by the L and X conduction band edges. From our data we obtain the following bowing parameters: CL = 0.10 ± 0.05 eV, Cx = 0.21 ± 0.07 eV for In1-xGaxAsyP1-y; CL = 0.4-0.7 eV, Cx = 0.08 ± 0.05 eV for In1-xGaxAs; and CL = 0.33 ± 0.05 eV, Cx = 0.13 ± 0.06 eV for In1-xGaxSb.

The use of the pseudo-Brewster and other reflection-transmissicn techniques in the characterization and interpretation of high temperature optical properties has been reported. In the pseudo-Brewster method one measures the ratio between the parallel and perpendicular to plane of incidence reflectance intensities at its minimum value, and the angle of incidence at that minimum to determine the optical coefficients n and κ. At high temperatures, where a surface oxide may build up during the measurement, operation under non-oxidizing conditions was required. A vacuum reflectometer, capable of operation at 500°C, is described. The variation in thickness of the surface oxide is small enough so as to be ignored in the pseudo-Brewster analysis, but would have introduced a larger error if an ellipsometric technique was employed. Results for n and κ of single crystal and amorphous germanium at temperatures up to 400°C are discussed in terms of the corresponding room temperature spectra. Extension of this point-by-point technique to a large spectral range has been suggested recently and is described. Conventional thin film transmission and reflection measurements have been utilized as complementary techniques to determine respectively the absorption edge and the subgap dispersion in the refractive index at high temperatures. The former results join smoothly with the pseudo-Brewster results. The temperature dependence of the refractive index dispersion and of the absorption edge, which are related by the Kramers-Kronig integrals, were compared via calculation of the moments of ε2, yielding good agreement between both kinds of measurements.

In the first part of this paper we describe some non-solar possible applications of semiconductor -liquid junction methodologies. These include: etching, photoetching, growth of a passivation layer, detection of metallic corrosion, electrochromic display devices, photodeposition of metals on semi-conductors and insitu characterization of semiconductor bulk properties. In the second part, we describe some of the methodologies used to characterize the semiconductor-liquid junctions. These include methods that were borrowed from electrochemistry and solid state photovoltaic devices, in addition to more specific methods based on electric field modulation of system's response such as impedance, electroreflectance and modulated photoluminescence.

Ellipsometry and electrolyte-electroreflectance have been combined as a destructive probe of the Si/Si02/KOH system. Optical measurements were made in the 3-4 eV photon energy range. The optical and electrical properties of the substrate/oxide interface of anodic and thermal oxides have been studied during the oxide etching. Changes in the ellipsometric parameters and the electroreflectance response of the substrate have been interpreted in terms of stoichiometric changes and the presence of surface states in the connective region between the Si semiconductor and its oxide.

Ultrashort light pulses are used to study carrier dynamics in highly excited semiconductor materials. Picosecond pulses from a cw modelocked Nd:YAG laser create carriers and probe nonlinear (Auger) recombination in InGaAs and InGaAsP epilayers. Femtosecond continuum pulses from a dye oscillator/amplifier system monitor the spectral dynamics of free excitons in CdSe following optical excitation.

Nondestructive characterization of semiconductor surfaces and interfaces by the surface acoustic wave (SAW) technique is demonstrated and reviewed. In the past few years, the sensitivity and applicability of this method has been greatly enhanced by the introduction of a new delay line structure and the use of two beam spectroscopy. The monitored signal in the following experiments is the transverse acoustoelectric voltage (TAV). Two beam spectroscopy (both beams are monochromatic) is applied to GaAs, InP and CdS in order to reveal the subband gap energy level structures. The presented data on the subband gap interface states which are due to the intrinsic nature of the surface discontinuity or due to the interface with other materials (electrolyte, oxide, etc.) includes the following: 1) High resistivity GaAs surface states, the GaAs/oxide interface states and the effect of wet anodic oxidation in increasing the density of these states, 2) Exciton absorption and energy levels in GaAs, InP at low temperature and the observation of quenching effect on the absorption peak which is more pronounced in GaAs due to the higher interface states density, 3) Interface states at CdS/electrolyte junction which are enhanced by the photo anodization of CdS, working under short circuit current in a semiconductor liquid junction solar cell configuration. The new delay line structure enabled us to vary the surface potential via a small external DC field (comparable to C-V technique) while monitoring the TAV amplitude and transient time constants. Thus parameters such as generation lifetime, oxide charge, flat band voltage and surface generation velocity are experimentally determined for silicon wafers. Nondestructive depth profiling of the free carrier concentration and some of the above parameters are also demonstrated. Zero bias surface condition and the recombination center energy level within the silicon bandgap are determined. This technique is being presently applied to (HgCd)Te samples.

X-ray photoelectron spectroscopy (XPS) has many virtues as a surface analytical technique especially in its ability to provide both elemental and chemical information from an unperturbed surface. Its only disadvantage has been a lack of spatial resolution limiting its compatability with other surface techniques, such as Auger (AES) and Secondary Ion Mass Spectrometer (SIMS). Small area XPS analysis has been developed for VG ESCALAB MkII in order to improve the technique's spatial resolution so that it can be combined directly with AES and SIMS in a true multi-technique approach to surface analysis. The spatial ranges of the various surface anlytical techniques listed in Table I show that conventional XPS has a narrow range of analysis area size of between 1 mm and 10 mm diameter and this range is outside the normal operating dimensions of either AES or SIMS. The aim of this small area XPS development was to extend the range of XPS downwards into the range of 100 to 1,000 microns where range of interesting surface applications. It was found that the change from conventional to small area XPS could be made rapidly on ESCALAB MkII and that the instrument's electron and ion beams could be used to define the area of XPS analysis. With the analysis conditions so well defined, three completely different samples were confidently analysed. Finally, the inherent loss of signal which results from analysing small areas has been solved by the development of multi-array detection on ESCALAB.

The unique tunability and x-ray energies of synchrotron radiation can be exploited to determine new properties of semiconductor interfaces that are central to current electronics technologies. As device dimensions shrink, a microscopic understanding of the growth, extent and composition of semiconductor interfaces becomes key in advancing the state-of-the-art. In this paper, we illustrate the dramatic advances in the scientific exploration of interface properties by an example from the Si-Si02 system which utilizes the photon energy tunability of synchrotron radiation combined with the core electron energy tunability of Soft X-ray Photoelectron Spectroscopy (SXPS). While the Si-Si02 interface is one of the most technologically important and well-controlled electronic materials systems today, we show that a detailed description of the interface regions still eludes direct correlation with measured trapping levels in MOS devices. By "fingerprinting" the oxidation states of Si on an atomic scale, we explore the evolution of the interface, determine species which serve as connective regions between the structurally incompatible materials, and deduce possible interface defects which might accompany incomplete oxidation. Synchrotron radiation studies of such process-related aspects of semiconductor interfaces are central to the understanding and control of device characteristics.

In this review some basics of the transmission electron microscopy, the instrument, its operations and the types of scientific information obtainable from crystalline materials are first discussed and then some subjects pertaining to recent characterization of silicon are discussed. The subjects chosen are those that had outstanding impacts in technology and/or in science for which studies using the transmission electron microscope forms an indispensible part of the characterization efforts.

The Scanning Transmission Electron Microscope routinely forms a 0.5nm diameter probe of 100KeV electrons with a total current of about 1 nano-ampere. It therefore promises to extend to atomic interfaces techniques that have been routinely used in the SEM for micron sized interfaces. An example of As segregation to grain boundaries in poly-crystalline Si is presented to show the strengths and weakness of the present STEM EDS systems. Electron energy loss scattering under the rather special conditions encountered in the STEM is reviewed. This technique promises a spatial resolution that is comparable to the probe size. But the interpretation of the inelastic scattering is complicated by the complex spatial frequencies which are present in the probe, and by the coupling of these frequencies to those in the probed system. The spatial quantization of the bulk plasmon within a small metal sphere is observable using this effect. When the probe passes close to, but not through, a small object, finite coupling can occur to produce energy loss. Surface plasmons with strong dipole symmetry have been observed at optical frequencies in 20nm sized systems with the STEM. Finally, these techniques should be extendible to electronic properties with the advent of new higher energy resolution electron spectrometers. A Wien filter capable of 0.2eV resolution and an accuracy of 20meV over a 1KeV range is described briefly.

The modern scanning electron microscope (SEM) provides the basis for a wide variety of techniques which are valuable for semiconductor characterization. These techniques cover the range of basic semiconductor materials characterization to live-time device characterization of operating LSI or VLSI devices. This paper will introduce many of the more commonly used techniques, describe the modifications or additions to a conventional SEM required to utilize the techniques, and give examples of the use of such techniques. First, the types of signals available from a sample being irradiated by an electron beam will be reviewed. Then, where applicable, the type of spectroscopy or microscopy which has evolved to utilize the various signal types will be described. This will be followed by specific examples of the use of such techniques to solve problems related to semiconductor technology. Techniques to be emphasized will include: x-ray fluorescence spectroscopy, electron beam induced current (EBIC), stroboscopic voltage analysis, cathodoluminescence and electron beam IC metrology. Current and future trends of some of these techniques, as related to the semiconductor industry, will be discussed.

The main concepts in ion scattering analysis of interfaces are reviewed and relevant literature is cited. High energy ion scattering has played an important role in the evolving understanding of semiconductor interfaces. A number of extensive reviews describe the fundamentals of this technique and its application to the study of semiconductor interfaces. The main purpose of this paper is to provide the reader with a guide to the existing literature on the subject. This brief review has been published in a similar form for the Materials Research Society Symposium on Interfaces and Contacts, 1982.

We present here a direct measurement of proton energy-loss straggling in Gal-xAlxAs/GaAs, enabling us to take maximum advantage of the 27Al(p, γ)28Si nuclear reaction as a powerful technique for measuring Al profiles in these structures without the removal of sample material. As an illustration of the usefulness of the technique, we have observed and determined quantitatively an effect of substrate preparation on the Al concentration gradient at the GaAlAs/GaAs interface. Results were obtained using samples produced by molecular beam epitaxy and fabricated to have step-function Al concentration distributions to prescribed depths. The exact straggling width was obtained by a least squares comparison of the experimental spectra with curves calculated using a parameterized straggling distribution. Profiling measurements can now be made, using these straggling results, to give the Al concentration fall-off at the interface region in GaAlAs/GaAs to about 4% and epilayer thickness determination to about 2%. These results are also applicable to the profiling of structures such as graded band gap GaAlAs/GaAs solar cells which are constructed to have continuously varying Al concentration gradients. The technique can also be extended to other related materials such as GaAlSb/GaSb.