arXiv subjects

Jiaqing Yue

Publications and source records attributed to Jiaqing Yue.

3 recordsLinked to original sources

arXiv2026

Kinetically Controlled Condensation Boundary Governing Indium Incorporation in InGaN Metal Organic Vapor Phase Epitaxy

We combine in situ synchrotron X-ray crystal truncation rod measurements with a binary Burton-Cabrera-Frank model to quantify indium incorporation during InGaN growth by metal-organic vapor phase epitaxy (MOVPE) on GaN(0001). By distinguishing In adatoms from condensed droplets and incorporating coupled Ga-In incorporation kinetics, the model captures the intrinsically nonlinear dependence of indium composition on precursor flux and growth temperature. The critical In coverage corresponding to the maximum attainable In composition at a given temperature is determined by a kinetic balance between In adatom supply and incorporation capacity, defining a kinetically controlled condensation boundary that shifts with temperature and Ga flux. The model quantitatively predicts this boundary, in agreement with independent measurements, and provides a predictive framework for optimizing high-In-content InGaN growth while avoiding droplet formation.

cond-mat.mtrl-sci↗

arXiv2026

Step- and terrace-resolved crystal truncation rod scattering from vicinal surfaces under coherent heteroepitaxy

We develop a general theory of crystal truncation rod (CTR) scattering from vicinal surfaces with a coherently strained heteroepitaxial film. The formalism incorporates film-induced interference fringes, full elastic lattice distortion, terrace ordering, surface reconstruction, and real-time growth evolution within a unified description. Comparison between Nagai model and elasticity-based model shows that the lattice tilt is nearly identical in the two approaches, whereas the elasticitybased model predicts an additional triclinic deformation arising from shear strain. This deformation has little effect on specular CTRs but strongly modifies non-specular rods, making them a sensitive probe of the full elastic state of coherent epitaxial films. We further show that the characteristic sensitivity of vicinal CTRs to terrace ordering, surface reconstruction, and terrace-resolved compositional modification remains robust in the presence of a coherent film. Representative calculations for InGaN/GaN demonstrate that the framework enables quantitative interpretation of both static and real-time CTR measurements and provides access to step- and terrace-resolved structural and kinetic information during heteroepitaxial growth.

cond-mat.mtrl-sci↗

arXiv2024

Computational Graph Representation of Equations System Constructors in Hierarchical Circuit Simulation

Equations system constructors of hierarchical circuits play a central role in device modeling, nonlinear equations solving, and circuit design automation. However, existing constructors present limitations in applications to different extents. For example, the costs of developing and reusing device models -- especially coarse-grained equivalent models of circuit modules -- remain high while parameter sensitivity analysis is complex and inefficient. Inspired by differentiable programming and leveraging the ecosystem benefits of open-source software, we propose an equations system constructor using the computational graph representation, along with its JSON format netlist, to address these limitations. This representation allows for runtime dependencies between signals and subcircuit/device parameters. The proposed method streamlines the model development process and facilitates end-to-end computation of gradients of equations remainders with respect to parameters. This paper discusses in detail the overarching concept of hierarchical subcircuit/device decomposition and nested invocation by drawing parallels to functions in programming languages, and introduces rules for parameters passing and gradient propagation across hierarchical circuit modules. The presented numerical examples, including (1) an uncoupled CMOS model representation using "equivalent circuit decomposition+dynamic parameters" and (2) operational amplifier (OpAmp) auto device sizing, have demonstrated that the proposed method supports circuit simulation and design and particularly subcircuit modeling with improved efficiency, simplicity, and decoupling compared to existing techniques.

math.NA↗