InGaAs-OI Substrate Fabrication on a 300 mm Wafer
In this work, we demonstrate for the first time a 300-mm indium–gallium–arsenic (InGaAs) wafer on insulator (InGaAs-OI) substrates by splitting in an InP sacrificial layer. A 30-nm-thick InGaAs layer was successfully transferred using low temperature direct wafer bonding (DWB) and Smart CutTM technology. Three key process steps of the integration were therefore specifically developed and optimized. The first one was the epitaxial growing process, designed to reduce the surface roughness of the InGaAs film. Second, direct wafer bonding conditions were investigated and optimized to achieve non-defective bonding up to 600 °C. Finally, we adapted the splitting condition to detach the InGaAs layer according to epitaxial stack specifications. The paper presents the overall process flow that achieved InGaAs-OI, the required optimization, and the associated characterizations, namely atomic force microscopy (AFM), scanning acoustic microscopy (SAM), and HR-XRD, to insure the crystalline quality of the post transferred layer.
Influence of implantation temperature on the formation of hydrogen-related defects in InP
The evolution of hydrogen-related defects introduced in the InP lattice due to the implantation and subsequent annealing is investigated as a function of the implantation temperature, that was varied from -15 °C to 230 °C. Implanted and annealed samples were analyzed by optical microscopy, SIMS and FTIR. The obtained results are discussed in terms of the formation of VInHx complexes that seems to be efficient H trapping centers, probably being the precursors of the fracture process in InP.
Numerical analysis of surface crack propagation in flexible pavements using XFEM and cohesive zone model
Surface initiated (top-down) cracking in the longitudinal direction of pavements has become a predominant mode of failure in thick asphalt pavements. Most previous researchers studied crack propagation using the traditional Linear Elastic Fracture Mechanics (LEFM) method by calculating the stress intensity factor around the crack tip. In this paper, Extended Finite Element Method (XFEM) was used to study the key factors causing surface initiated crack propagation under surface tension and/or shear. A two-dimensional (2-D) finite element (FE) model for a two-lane flexible pavement was built to predict pavement responses and crack propagation potential under various scenarios. It was found that surface tension is the major driving force for crack propagation when the crack is at some distance away from tire loading. The results show that the distance from the location of crack to tire loading, the depth and direction of the crack, and the modulus ratio between the hot-mix asphalt (HMA) layer and the base layer have significant influences on crack propagation under surface tension. On the other hand, this study shows that shear stress can induce surface initiated crack propagation near the loading area as the shear resistance of material becomes low at the high temperature.