EEPROM charge monitors reveal that an O2 plasma induces a negative charge which peaks at the wafer center for the asher used. The charge damage to small gate area MOS capacitors is investigated by using “antenna” structure. The post plasma interface state density increases with increasing antenna size and varies by two orders of magnitude. A hole trapping induced breakdown mechanism during plasma charging is supported by new experimental evidence such as the annealing and polarity effects of charge-to-breakdown and tunneling currents. Where stressing has not being severe, these hole traps are annealable at T > 650°C, while in severely stressed areas early breakdown occurs which is not annealable.

In this paper we show that when grown by MBE at unusually high temperatures epitaxial layers of GaSb and GaAs are semi-insulating. In GaSb combination of Hall effect, TSC, SIMS and two probe resistivity profiling leads us to believe that high resistivity is due to production of midgap centers at elevated temperatures. No strong evidence of the prevalence of such midgap centers was obtained for high temperature GaAs layers and in this case we believe that high resistivity is associated with the formation of Ga-related precipitates acting as internal Schottky barriers.

A Transmission Electron Microscopy (TEM) study on ALMBE grown InAs/GaAs (001) is presented. The density and the types of defects contained in InAs and GaAs layers are clearly different. A relation between the planar defects in these layers and the compressive and extensive nature of the growth for each layer is found. Atomic Layer Molecular Beam Epitaxy (ALMBE) grown InAs layers possess a better quality of defects than other InAs layers grown on GaAs (001) by conventional MBE. Several ways of nucleation are presented as possible for explaining the existence of the different defects found in the studied heterostructure.

A detailed optimization of MBE growth of CdTe on CdTe (111)β using white beam synchrotron x-ray topography, and x-ray rocking curve analysis has been carried out. Defect structures in (111)5 substrates and epilayers are imaged with white beam topography and, for the first time, direct observation of stress induced microtwin growth in CdTe epilayers has been made. X-ray rocking curve analysis of CdTe substrates is shown to be relatively insensitive to defect structures consisting of dislocations and inclusions. On the other hand rocking curve analysis of (111) epilayers reveals a sensitivity to the presence of microtwin. The defect microstructure of a CdTe (111)Bepilayer with the narrowest rocking curve FWHM value published to date (9.4 arc-sec) will be discussed.

In this work, a method of obtaining mosaic spread of the heteroepitaxial structures using Renninger scan (RS) peak profiles is reported. A simulation program was developed in order to account for the influence of the wavelengths, incident beam divergence, sample mosaic spread (layer and substrate) in the profile of the RS peaks. Surface three beam multiple diffraction cases with a forbidden or even very weak primary reflections are used to provide simpler intensity expressions and high intensity in RS. GaAs/Si samples have been analyzed as an application of this method.

Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self- interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.

Ion-assisted doping of homoepitaxial p-CdTe films with low energy P ions (20 eV) deposited by vacuum evaporation has been investigated. In order to control the properties of the films, we applied low energy electron irradiation and Cd overpressure during the growth. We report the results of measurements of hole density, spectral response of Cr/p-CdTe Schottky barriers (to estimate the minority carrier diffusion length Lj). From Ld, we have found that the quality of the films is dependent on both the ion dose and the ion energy. By reducing the ion energy to 20 eV and applying electron irradiation and Cd overpressure, p-CdTe films with p = 1 × 10 17 cm−3 and Lp =0.35 μm were obtained. A p-CdTe film with p = 1016 cm−3 was obtained with a low ion energy of 10eV.

In this paper we provide a review of materials issues in the III-V alloy semiconductor system and examine the role of such issues in the degradation of semiconductor lasers and LEDs.

Among the major materials issues are the formation of defects and thermal instability of the crystals; we will discuss both of these processes, giving relevant examples. It is convenient to divide crystal defects into two classes: interface defects are bulk defects. Among the former type of defects are stacking faults, V-shaped dislocations, dislocation clusters, microtwins, inclusions and misfit dislocations. Defects belonging to the second class include precipitates and dislocation loops. Thermal instability in crystals during growth also leads to structural imperfections which can affect device properties. One example is the formation of quasi-periodic modulated structures due to spi nodal decomposition of the crystal either at the liquid/solid interface or the growth surface. Another is the formation of ordered structure which also occurs on the growth surface through migration and reconstruction of deposited atoms.

We discuss optical device degradation in terms of three major degradation modes: rapid degradation, gradual degradation and catastrophic failure. In devices which degrade by rapid degradation, it is found that recombination-enhanced dislocation glide and climb are responsible. We examine the ease with which these phenomena occur in various hetero-structures and attempt to determine what the dominant parameters are. Gradual degradation takes place presumably due to recombination-enhanced point defect reaction in GaAlAs/GaAs-based optical devices. This degradation mode can be enhanced by the presence of stress due to lattice mismatch in the system. However, in InGaAsPAEnP-based devices, gradual degradation is not observed. In GaAlAs/GaAs DH lasers, catastrophic failure is found to be the result of catastrophic optical damage at a mirror or defect. Again, however, InGaAsP/InP DH lasers do not suffer from this form of degradation. In each degradation mechanism, the role of defects in the degradation and methods of elimination of degradation are discussed.

Atomic structures of planar defects in Si and GaAs have been studied by TEM. An HREM image of the edge of {113} planar defect has been obtained with <110> incidence. An analysis of the image has showed diat the edge consists of 5-, 6- and 7-membered rings without dangling bond. Anisotropie morphology of the defect could be understood from the model proposed in this report. Weak diffuse scattering and an extinction rule in diffraction patterns from the defect have been found. The experimental evidence has supported the model of the {113} defect.

A planar defect on {111} in a heavily Si doped GaAs has been studied. The result has indicated that Si precipitates on the two {111} net planes inserted in the GaAs matrix.

Nondestructive characterization techniques for substrates, epilayers, and device structures are becoming increasingly important in the semiconductor industry. Synchrotron-based white-beam x-ray topography, x-ray rocking curve measurements, and etch pit density were used to map the defect structure in a variety of CdTe and CdZnTe single crystal substrates, which are important for IR detector applications involving HgCdTe. Defects such as low angle grain boundaries have been successfully correlated using topography, rocking curves, and etch pit density, and twins have been observed using topography and rocking curves. The effectiveness of white-beam synchrotron topography for rapid and nondestructive defect analysis and substrate screening is discussed.

Dislocations and point defects introduce energy levels deep in the gap, which dramatically change the material electrical properties. Because of the coexistence of a multitude of dislocation types and dislocation-point defect interaction mechanisms, it would be highly desirable to identify the particular type of defect related to specific traps.

The electrical activity of extended defects (planar precipitates and dislocations) is here examined in terms of their recombination activity, investigated by electron as well as light beam induced current methods of scanning microscopy.

Besides, a scanning modification of spectroscopy is used to identify traps at individual defects. The method, named quenched infra-red beam induced current, combines the scanning light beam induced current technique with the spectroscopie bulk analysis called “infrared quenching of photoconductivity”.

Defect energy levels are found on the basis of the particular features of the beam induced current as a function of injected carrier generation rate, temperature and quenching excitation.

Slow/monoenergetic positron beams and pulsed positron beams have been used as a non-destructive probe to investigate vacancy-type defects in SIMOX substrates which were formed by high - dose oxygen implantation and high-temperature annealing. To obtain depth profiles of vacancy-type defects, a positron beam in the 0–30keV energy range was used. Doppler broadened annihilation spectrum and positron lifetime were measured as a function of incident positron energy. These measurements show the following results; vacancy -type defects exist near the surface of the top silicon layer even if the specimen was analyzed as defect -free Silicon by XTEM, and in the case of the as-implanted specimen, cavities in diameter of about 50–200A are created in the top silicon layer and they include high pressure gases.

Hydrogen is commonly used in crystalline Si for passivation of defects and impurities. When single crystal Si undergoes a post-hydrogenation step, hydrogen-induced platelets have been shown to form in the first 100 nm of the Si. The same hydrogen platelets occur in homoepitaxial Si grown by low temperature (350°C or below) plasma-enhanced chemical vapor deposition with hydrogen dilution. This study has used transmission electron microscopy (TEM) to examine the structure of these hydrogen-induced platelets. TEM has shown that the platelets generally grow in tne (111) crystal planes of the Si. The size of the platelets, which ranges from 5 to 100 nm, increases with growth temperature but the density of platelets decrease at higher growth temperatures. The hydrogen platelets are not confined to the epitaxial Si layer only but also grow into the substrate. High resolution TEM shows the platelets dilate the silicon lattice by approximately 60% of a Si <111> plane. TEM has also shown that platelets cause no net displacement of the local Si lattice. Tilting experiments performed in the TEM show that the platelets are composed of a circular two-dimensional structure. Our results indicate that the hydrogen-induced platelets found in low temperature epitaxial Si are structurally the same as those seen in crystalline Si that has undergone post-hydrogenation processes.

Photoluminescence (PL) and deep level transient spectroscopy (DLTS) measurements have been carried out on Si1-xGex/Si heterostructures and Si/Si1-xGex/Si double heterostructures with fully strained or partially relaxed layers (0%<xGe<20%) grown by chemical vapor deposition using rapid thermal processing (RTCVD). This study reports strong PL and DLTS results connected to the establishment of relaxation defects in the SiGe layer and at the heterointerface which appear when the layer starts to relax. Strong broad PL bands (defect related) and sharp lines (similar to dislocation related D-lines on Si) have been detected and connected to this relaxation process. These PL results are strengthened by the clear observation, using DLTS experiments on relaxed layers, of interface traps with a maximum energy around Ev + 0.5eV resulting from the presence of misfit dislocations at the SiGe/Si hetero-interface and a deep level at Ev + 0.38eV related to dislocations or relaxation defects in the SiGe layer. Moreover, low temperature PL excitonic transition reported on Si/Si1-xGex/Si double heterostructures is described as a good tool to investigate the relaxation process which occurs in these heteroepitaxial layers.

Previous results [1] have shown that type II (end-of-range) dislocation loops can be used as point defect detectors and are efficient in measuring oxidation induced point defects. This study investigates the interaction between oxidation-induced point defects and dislocation loops when Ge+ implantation was used to form the type II dislocation loops. The type II dislocation loops were introduced via Ge+ implants into <100> Si wafers at 100 keV to at doses ranging from 2×1015 to l×1016/cm2. The subsequent furnace annealing at 900 °C was done for times between 30 min and 4 hr in either a dry oxygen or nitrogen ambient. The change in atom concentration bound by dislocation loops as a result of oxidation was measured by plan-view transmission electron microscopy (PTEM). The results show that the oxidation rate for Ge implanted Si is similar to Si+ implanted Si. Upon oxidation a decrease in the interstitial injection was observed for the Ge implanted samples relative to the Si implanted samples. With increasing Ge+ dose the trapped atom concentration bound by the loops actually decreases upon oxidation relative to the inert ambient implying oxidation of Ge+ implanted silicon can result in either vacancy injection or the formation of an interstitial sink.

The influence of the Al concentration in the X-Ray Renninger scans (RS) for the GaAlAs/GaAs system is investigated. The RS simulation program MULTX [Defect Control in Semiconductors, K. Sumino (ed.) Elsevier Sci. Pub. (North Holland), 1990, 1535] allows for the better choice of peak/background ratio which shows enough sensitivity to detect Al content changes. The three (000, 002, 111) and four beam (000, 002, 113, 111) peak/background ratios decrease with the increment of the Al content according to the structure factor calculation.

Analysis of the white beam synchrotron x-ray topographic contrast behavior of screw dislocations comprising slip bands in silicon, observed under low absorption conditions, is presented. For both individual and groups of dislocations, observed “Direct Image” contrast at the surface intersections of dislocation lines, on reflections for which g·b=0, could be accounted for using equi-misorientation contour analysis using displacement fields which take surface relaxation effects into account. This contrast is shown to be a sensitive function of the local stress environment. In addition, diffuse area contrast observed within and in the vicinity of slip bands on such reflections is also observed to be very sensitive to long range strain fields associated with adjacent slip bands and other defects in the local slip band environment.

Using FTIR-spectroscopy for the determination of the oxygen content in CZ Si, an additional absorption of IR light occurs for doping densities above 1015/cm3, which is caused by the free carriers. It increases nearly linearly with the carrier density and reduces multiple reflections within the sample. Excessively low oxygen values are obtained if this effect is neglected. The deviation from the true values can amount up to 15 % and depends on carrier density, type of doping, oxygen content and sample thickness. Measurements of the absorption coefficient induced by the free carriers were performed for p-and n-type FZ material in dependence of the IR wavelength and of the doping concentration. The obtained values at the wavelength of the oxygen absorption band (1107 cm−1) were used to calculate correction factors for the oxygen content in the doping range from 1 * 1017 to 1 * 1015/cm3. An example shows that the correction reaches 5 % for carrier densities of 1 * 1017/cm3, n-type and 2 * 1016/cm3, p-type, respectively, for an assumed sample thickness of 0.7 mm.

Native defects in Si-doped, Zn-doped and undoped GaAs grown by horizontal Bridgman (HB) method and molecular beam epitaxiy (MBE) were studied by a monoenergetic positron beam. Positron lifetime spectra and Doppler broadening profiles were also measured by using energetic positrons. It was found that monovacancies were usually found in Si-doped HB-GaAs, however, divacancies were created in a specimen with low impurity concentration. For Zn-doped HB-GaAs, interstitial clusters were found to be major type of defects. The high concentration of monovacancies and of divacancies coexist in heavily Si-doped MBE-GaAs. These vacancy-complexes were found to act to reduce the concentration of free carriers.

A monoenergetic positron beam has been used to investigate the state of interstitial oxygen in Czochralski (CZ)-grown Si with either thermally grown S1O2 (100 nm thick) or silicon oxide (p-SiOx) deposited by plasma enhanced chemical vaper deposition technique on the surface. Both the growth of thermal SiO2 and the deposition of SiOx film resulted in a reduction of the doppler-broadening line shape parameter (S-parameter) for the positron annihilation in the bulk silicon region. Annealing at 450δC, the removal of oxide overlayer or long-term aging at room temperature caused the S-parameter to return to its intrinsic value. It was thought that tensile stress in silicon, induced by the thermal oxidation or the deposition of SiOx films which had compressive internal stress themselves, enhanced the rearrangement of oxygen atoms and caused the formation of oxygen clusters in silicon crystal. Oxygen interstitial clusters can trap positrons leading to the lower S-parameter value for annihilation in the bulk silicon region, because of large overlap with core electrons. The above results suggest that oxygen atoms can absorb lattice strain by clustering and thus prevent the generation of dislocations against external stress in the Si lattice. This results yield an additional explanation of the high mechanical strength of CZ Si crystal.