Capacitance transient spectroscopy has been used to investigate the electrically active defects subsisting, after a ruby laser pulse annealing, in ion implanted silicon. In contrast to the common view, it is shown that the identified point defects are related to residual implantation related defects buried beyond the dopant distribution and not to the laser effect.

The luminescence properties of undoped GaAs-Ga1−x Alx As layers grown by liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) are compared for double heterostructure and multiquantum well (MQW) superlattices. Low temperature cathodoluminescence and scanning transmission electron microscopy are used to identify the main luminescence centers and in some instances establish their origin. The possible effects of the observed luminescence features on the degradation process in GaAs-Gal−x Alx As laser devices grown by MBE and LPE are also discussed.

Three examples pertaining to the influence of heavy doping on the microscopic perfection of as-grown InP crystals, thermal decomposition of InP crystals and epi-layers and optically induced degradation of InGaAsP epi-layers have been chosen to delineate some of the correlations observed between microstructure and properties in these materials. Itis shown that the macroscopic perfection can be significantly improved by highly doping with Zn, S, and Se. However, in the case of Zn, not all of the dopant atoms are in solid solution and some of them have clustered to form precipitates, whereas these features are not seen in highly S- and Se-doped crystals.

Thermal decomposition of epi-layers introduces areas which appear dark in a photoluminescence scan. It is argued that these regions evolve due to the out diffusion of P. In addition, when InP epi-layers are grown on thermally-decomposed substrates, dislocation density in the epi-layers is higher than that in the substrate. Arguments have been developed to rationalize these observations.

Non-luminescent regions develop in InGaAsP epilayers by optical pumping. These areas are associated with dislocation clusters which appear to evolve by glide of the existing dislocations.

Electronic defect levels have been measured in n-type epitaxial films of Gal - XAIXAs (0≤X≤0.33) which were grown by metalorganic chemical vapor deposition. Electron traps were characterized by transient capacitance spectroscopy on Schottky-barrier diodes. The thermal activation energy for electron emission from the near-midgap defect level is found to be larger in Ga1 - XAIXAs than the value of 0.83 eV generally observed in GaAs.

Uncapped and Si3N4-capped annealing of GaAs grown with the horizontal Bridgman technique was investigated with deep-level transient spectroscopy. Electron trap concentration distributions were measured with a reduced noise DLTS system to ensure reliable data. Ion implantation using Se ions both prior to capping and through a Si3N4 cap was carried out. The evolution of defect energy levels and the changes in concentration distributions with anneal temperature were studied. It is concluded that the defects residing in the probed space-charge region can be annealed out with a Si3N4 cap at a temperature higher than 750 C.

The dark capacitive transients related to the main electron trap in bulk and VPE GaAs have been studied in detail. The low temperature low field transients are induced by electrons injected from the metal counter electrode. Both hot electron capture and impact ionization effects are observed. At high fields, a phonon assisted tunneling model accounts for the observations and yields the values of the Franck Condon Shift Sw and the energy w of the phonon coupled to the level. These values are found to be in good agreement with other independent estimates.

The defect structure of cadmium telluride has been investigated using high resolution transmission electron microscopy. The variation of the TEM images with the defocus value is discussed, and defect symmetry considerations are used to correlate the image contrast characteristics with the lattice struc ture. Experimental micrographs of stacking faults and dislocations in the structure are analyzed.

Scanning cathodoluminescence microscopy (SCM) has been used for nondestructive characterization of the optoelectronic properties of heavily Zn-doped, Bridgman-grown polycrystalline GaAs. Grain boundaries can either show no cathodoluminescence contrast, appear as dark lines, or appear slightly brighter than the surrounding matrix. Boundaries with similar surface morphologies can show different contrast. Spectral analysis data indicate that many of the observed features are due to local variations in impurity concentration.

Interaction of impurities with the “visible defects” in hot implanted Cr doped semi-insulating (100) GaAs has been investigated. The defects studies were performed using transmission electron microscopy (TEM) and MeV He+ channeled Rutherford backscattering. The defects distribution was obtained by 90° cross-sectional TEM (XTEM). The atomic concentration profiles of Se, and carrier-concentration and mobility profiles were obtained by secondary ion mass spectrometry (SIMS) and Hall measurements in conjunction with chemical stopping, respectively. Comparison of defects, atomic and electrical profiles, showed the formation of secondary defects at and beyond the projected range (Rp), a significant amount of Se+ diffusion beyond Rp, and compensation of electrical carriers caused mainly by the point defects present in hot implanted GaAs.

TEM and SEM studies have been carried out on a series of GaAs/GaInAs, InP/GaInAs and InP/GaInAsP device-type structures grown either by vapour phase epitaxy (VPE) or liquid phase epitaxy (LPE). By using the TEM high voltage electron microscope operating at 1000kV, a determination was made of the nature, origin and three-dimensional distribution of structural defects in these specimens (mainly dislocations and stacking faults). SEM EBIC and CL examinations were also performed to study the electrical and luminescent properties of these layers. The ultimate aim is to correlate structural information with electrical and luminescent properties, and with device performance.

The microstructure of commercially available reactionbonded polycrystalline SiC containing 8–10 wt% excess silicon was studied after irradiation by reactor neutrons uitlizing transmission electron microscopy (TEM) and scanning electron microscopy (SEM). For TEM studies on samples irradiated below 473°K we observe dislocation tangles near grain boundaries or impurities plus isolated dislocations throughout the remainder of the grain, whereas for irradiation temperatures of ≈3730°K the material exhibits copious quantities of “black spot” defects (2–5nm size) and a lower concentration of tangles than 473°K irradiation. The SEM studies of surfaces of samples fractured at 1473°K indicate that the mode of fracture is predominantly transgranular.