摘要:

We present data of the interdiffusion coefficient of AlGaAs/GaAs over the temperature range 750–1150 °C, and obtainEAandD0values of3.6±0.2 eVand 0.2 (with an uncertainty from 0.04 to 1.1)cm2/s,respectively. These data are compared with those from the literature taken under a wide range of experimental conditions. We show that despite the range of activation energies quoted in the literature all the data can be described using a single activation energy. Using this value ofEAto fit the published data and then determiningD0for each data point we find that the published data fall into two clusters. One, for samples annealed under a gallium rich overpressure and a second for As rich or capped anneals. This result can be explained by the diffusion in all cases being governed by a single mechanism, vacancy-controlled second-nearest-neighbor hopping. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366345

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Diffusion barrier properties of nanostructured amorphous Ta-Si-N thin films with different N concentrations have been investigated in metallurgical aspects of Cu metallization. When the N content exceeds 40 at. &percent;, the Ta-Si-N film remains in the nanostructure phase even after annealing at 1100 °C for 1 h and effectively prevents Cu diffusion after annealing at 900 °C for 30 min. The reason for the excellent thermal stability is that excess N atoms disturb the grain growth ofTaSi2phase and keep the Ta-Si-N film in the nanostructure phase during the high temperature annealing. The Ta-Si-N film with N content less than 40 at. &percent; fails to prevent the Cu diffusion after annealing at 700 °C for 30 min. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366346

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We apply a linear stability analysis to examine the effect of misfit stress on the interface diffusion controlled morphological stability of multilayer microstructures. The stresses could be the result of misfit strains between the individual film layers and/or between film and substrate. We find that misfit between the layers in the film can destabilize the multilayer structure in cases where the thinner layer is elastically stiffer than the thicker layer. The rate at which these instabilities develop increase with increasing misfit and decreasing interfacial energy. Even when there is no misfit between layers, the misfit between the multilayer film and substrate can destabilize the interfaces. This type of instability occurs whether the thinner layers are stiffer or more compliant than the thicker ones. By appropriate choice of the elastic moduli mismatch between layers and relative layer thicknesses, the presence of an interlayer misfit can suppress the instability caused by the substrate misfit. We present stability diagrams that can be used to design stable, multilayer films using all of the degrees of freedom commonly available in multilayer film deposition. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366347

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Strains in HgTe/Hg0.1Cd0.9Te superlattices grown on (211)B Cd0.96Zn0.04Te substrates have been investigated by high-resolution x-ray diffraction. The lattice mismatch, the tensile as well as the shear strain have been obtained by measuring symmetric and asymmetric diffraction profiles in different azimuths. These measured strain parameters are then used to extract from the diffraction profiles the chemical composition and thickness of individual layers constituting the superlattice period. The analysis is based on the theory of elasticity, in which the strain tensor components in partially relaxed epitaxial layers are calculated by minimizing the strain energy density. The method presented in this article is valid for the strain analysis of partially relaxed epitaxial layers grown on arbitrarily oriented surfaces. ©1997 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.366399

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Strain relaxation behavior inIn0.2Ga0.8As/GaAsmultiple quantum well (MQW) structures with various barrier thicknesses but with fixed well thickness was characterized by analyzing the x-ray rocking curves and low temperature photoluminescence. For the thick-barrier samples which have good optical characteristics, it is observed that the superlattice x-ray peaks are broadened nonuniformly. This anomalous behavior can be successfully simulated by considering the paired dislocation character in the double-kink type strain relaxation. Meanwhile, the thin-barrier ones show deteriorated optical properties which can be attributed to dislocations located at the MQW-substrate interface. This observation shows that two different relaxation mechanisms are working for the thick- and thin-barrier cases, respectively. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366348

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Transmission electron microscopy (TEM) has been used to investigate the mechanisms of misfit strain relaxation inInxGa1−xAsepilayers grown onGaAs(111)Bsubstrates misoriented 2° towards[211].It was found that the relaxation was brought about by a triangular network of misfit dislocations lying along the three ⟨11¯0⟩ directions near the interface. However, the dislocation distribution was anisotropic with a much higher density of dislocations lying parallel to the [01¯1] direction. A second relaxation mechanism was also observed which involved the formation of deformation twins. These had nucleated at the epilayer surface and grown down into the epilayer, sometimes entering the underlying buffer layer. Twin formation was also anisotropic with twins forming on the (1¯11)[211] system only. The dislocation and twin anisotropy may not be explained using the Schmid Factor considerations but is thought to be associated with heterogeneous nucleation of dislocations at the [01¯1] surface steps caused by the misorientation. The critical layer thickness for the observation of misfit dislocations by TEM inIn0.25Ga0.75As(111)Bepilayers was found to be between 15 and 25 nm. This is the same range as that observed for (001) epilayers of the same composition. This is as expected from theoretical considerations of the effects of orientation on the elastic modulus and the strain relieving component of the misfit dislocation Burgers vector. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366349

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The surface morphology and crystalline quality of GaN layers grown by metalorganic chemical vapor deposition on sapphire (0001) substrates were investigated for various thermal treatment conditions of low-temperature (LT)-grown GaN buffer layers. The surface morphology and crystalline quality of subsequently grown high-temperature (HT) GaN layers strongly depended on thermal effects during the temperature ramping process after LT growth of the buffer layers. We have found that the defect density and structure are affected by this temperature ramping process, and that the generation of growth pits is closely related to defects in the HT-GaN layers. High-quality HT-GaN layers with specular surface morphology were obtained with optimum growth and ramping conditions for the LT-GaN buffer layers. Furthermore, the role of thermal treatment during the temperature ramping process was identified, and mechanisms of nucleus formation, HT-growth initiation on the LT-GaN buffer layers, and defect formation are proposed and discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366350

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

InP was grown by chemical beam epitaxy in narrow windows of widths varying between 20 and 2 &mgr;m, oriented along the [011] or [01¯1] directions opened in aSiO2mask on an (001) InP substrate. Several facets appear along the sidewalls and on the edge of the mesas owing to different growth rates on different crystallographic planes. These can be understood as consequences of the migration of group III species from one crystallographic plane to another. We have studied the formation of such facets and their effects on the growth of GaInAs/InP structures of various thicknesses. The samples were studied using a field emission scanning electron microscope (SEM) and low temperature photoluminescence (PL). SEM micrographs show that for lines oriented along the [011] direction the dominant InP sidewall facets are (111)Bplanes on which GaInAs does not grow as long as Ga and In species can migrate towards (001). For the orthogonal direction, however, the lateral growth rate of the InP sidewalls is large and the faceting of the mesas is more complicated. The PL spectra of GaInAs quantum wells grown on such mesas exhibit several peaks whose energy depends on the initial width of the mask. They can be interpreted in terms of crystallographic plane dependent migration and desorption rates of Ga and In species. The (111)Bfacets of [011] directed mesas were used to produce inverted V-shaped mesa wire structures. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366351

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Hg1−xCdxI220–25-&mgr;m-thick layers with a uniform composition in the range ofx=0.1–0.2were grown on CdTe substrates by vapor phase epitaxy (VPE). The growth was carried out using an&agr;-HgI2polycrystalline source at 200 °C and in the time range of 30–100 h. The layers were studied by scanning electron microscopy (SEM) and high resolution synchrotron x-ray topography (SXRT). The SEM and SXRT images ofHg1−xCdxI2VPE layers allow one to identify the defects affecting the layer structure. The two main types of structural defects in the layers are subgrain boundaries and densely spaced striations similar to those referred generally to as vapor grownHgI2bulk crystals. The effect of the growth time on these defects has been analyzed and on the basis of this it has been possible to growHg1−xCdxI2layers with low defect density.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366352

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Wafer bonding is increasingly used to fabricate heterostructures which cannot be obtained by conventional epitaxial growth because they involve highly mismatched materials. We have optimised the GaAs/InP bonding process in order to realise long wavelength microcavity devices combining advantageously high reflectivity AlGaAs Bragg reflectors with an InP-based active material. The bonded interface has been studied by transmission electron microscopy. Three dislocation networks are found at the interface. The first one accommodates both the lattice mismatch and the inevitable twist between the two crystals whereas the second one accommodates the tilt resulting from the slight vicinality of the initial surfaces. Our experiments strongly suggest that the third network forms upon cooling the structure. Between the dislocation lines, the crystal structure is perfectly reconstructed across the interface, with no amorphous materials present, except for cavities which occupy a few percent of the bonded area. The geometry and distribution of these cavities can be studied by imaging the first dislocation network. In light of these results, we discuss the mechanisms operating during the formation of the interface. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366353

出版商:AIP    

年代:1997

数据来源: AIP