Structural and optical properties of strainrelaxed InAsP/InP heterostructures grown by metalorganic vapor phase epitaxy on InP(001) using tertiarybutylarsine We have investigated the strain relaxation of intentionally lattice mismatched (Ϯ0.5%͒ GaInP layers grown on GaAs substrates by organometallic vapor phase epitaxy. Double axis x-ray diffraction was used to measure the relaxation in these epitaxial layers in perpendicular ͗110͘ directions as a function of thickness. For samples in tension, the difference in relaxation between ͓110͔ and ͓110͔ increases from 10% to 48% as the layer thickness increases from 7 to 28 times the critical thickness, h c . For samples in compression this difference is 28% at 24h c while no relaxation is measured for a sample at 6h c . These results indicate that strain relaxes anisotropically and that the anisotropy is more pronounced for samples in tension than in compression. Furthermore, the major relaxation axis was found to be ͓110͔ regardless of the sign of the strain. Reciprocal space maps, generated using triple axis x-ray diffraction, showed that the amount of microtilt of the epitaxial layers was also anisotropic. This anisotropy and the direction of the maximum dislocation density which was measured by cathodoluminescence and transmission electron microscopy, changed from ͓110͔ in tension to ͓110͔ in compression. The fact that the major relaxation axis remained stationary while the high misfit dislocation density direction rotated indicates that a substantial number of dislocations with Burgers vectors of the ''wrong sense'' for strain relief are formed in compressed epilayers. A model in which ␣ type dislocations are more mobile than the ␤ type misfit dislocations regardless of the sign of the strain is consistent with all of the experimental observations.

No abstract

A method for measuring the mean free path of laterally gliding threading dislocations, based on the growth of lattice mismatched epitaxial layers on patterned substrates has been presented. The method requires no post growth annealing and permits an accurate measurement of the glide process as it occurs during epitaxial growth. This method has been applied to an InGaAs/GaAs heterostructure with a lattice mismatch of 0.5%. Mean free paths of 960 μm for α type dislocations and 1000 μm for β type dislocations were measured. It was concluded that the interaction of threading dislocations with clusters of misfit dislocations and/or edge type dislocations was the primary mechanism of glide length attenuation.

Short-period Ga0.51In0.49P/GaAsyP1−y strained superlattices were grown, by organometallic vapor phase epitaxy, with periods around 70 Å and phosphorus compositions from 0.04 to 0.31. Ground state emission as high as 1.73 eV was observed. Model solid theory predictions fit this data well, particularly at lower P compositions. Type II structures were obtained for phosphorus compositions above 0.04. The introduction of phosphorus in the low bandgap regions of these superlattices was found to significantly improve their structural and optical quality. These superlattices provide, in many applications, a viable alternative to the quaternary alloy GaInAsP, which is required for obtaining these bandgaps in Al-free systems lattice-matched to GaAs. To our knowledge this is the first report on the growth and modeling of short-period superlattices using this material system.

Deep level transient spectroscopy, (DLTS) and cathodoluminescence (CL) were used to study the hydrogen passivation of misfit dislocations in In,,, Ga0,4As/GaAs heterostructures. The CL observations indicate that hydrogen plasma exposure passivates most, but not all, of the dark line defects existing iti the specimen prior to hydrogenation. The concentration of deep level defect states that cannot be passivated is below the detection limit of the DLTS instrument [approximately 4X 1012 cmw3). We find the passivation is stable after anneals at temperatures as high as 600 'C, indicating that hydrogen passivation of misfit dislocations is at least as stable as that of the isolated point defect studied previously with