arXiv subjects

Xinjing Guo

Publications and source records attributed to Xinjing Guo.

4 recordsLinked to original sources

arXiv2026

Nonradiative Multiphonon Model of Deep-Level Transient Spectroscopy: Beyond Henry-Lang Model

Deep-level transient spectroscopy (DLTS) is a key experimental method for defect characterization, yet its analysis remains controversial, and the two widely used models developed by Henry and Lang are conflicting. We show that the Henry-Lang model is valid only under the Condon approximation, as well as high-temperature and strong electron-phonon coupling approximations, which cause incorrect temperature dependence of carrier emission and capture. Here we develop a rigorous nonradiative multiphonon (NMP) model, and demonstrate that the temperature dependence is governed predominantly by effective phonons with large phonon wavefunction overlap and high thermal occupation. The effective phonons are strongly correlated with lattice relaxation.The neglect of this correlation in existing DLTS models introduces substantial errors when they are used to fit DLTS-measured emission rates. Our comparison for 21 different defects in 12 semiconductors, including Si, SiC and Ga$_2$O$_3$, shows that the Henry-Lang model gives a completely different temperature dependence of carrier capture cross section from that obtained using the rigorous NMP model, with errors reaching up to six orders of magnitude at room temperature. Our study highlights the necessity of revisiting previous DLTS analysis studies using the rigorous NMP model.

cond-mat.mtrl-sci↗

arXiv2026

RASP: Reliability ab initio simulation package of MOSFETs based on all-state model

As transistors continue to scale down, device reliability has become a critical concern. In order to accurately simulate defect-induced reliability degradation in MOSFET based logic, memory and power devices, we develop RASP (Reliability Ab initio Simulation Package), which implements the all-state model for reliability simulation. Unlike conventional two-state and four-state models that consider only two and four defect configurations respectively, the all-state model systematically considers all possible defect configurations in amorphous gate dielectrics and all nonradiative multiphonon (NMP) and thermal transition pathways among them. With defect parameters obtained from ab initio calculations as input, RASP enables accurate simulation of threshold voltage shifts caused by defects. Using RASP to simulate oxygen vacancies in a-SiO$_2$, we find that they are a non-negligible source of negative bias temperature instability (NBTI).

cond-mat.mtrl-sci↗

arXiv2024

Si/SiO$_\text{2}$ MOSFET Reliability Physics: From Four-State Model to All-State Model

As implemented in the commercialized device modeling software, the four-state nonradiative multi-phonon model has attracted intensive attention in the past decade for describing the physics in negative bias temperature instability (NBTI) and other reliability issues of Si/SiO$_\text{2}$ MOSFET devices. It was proposed initially based on the assumption that the oxygen vacancy defects (V$_\text{O}$) in SiO$_\text{2}$ dielectric layer are bistable in the Si-dimer and back-projected structures during carrier capture and emission. Through high-throughput first-principles structural search, we found V$_\text{O}$ on non-equivalent O sites in amorphous SiO$_\text{2}$ can take 4 types of structural configurations in neutral state and 7 types of configurations in +1 charged state after capturing holes, which produce a wide range of charge-state transition levels for trapping holes. The finding contrasts the structural-bistability assumption and makes the four-state model invalid for most of O sites. To describe the reliability physics accurately, we propose an all-state model to consider all these structural configurations as well as all the carrier capture/emission transitions and thermal transitions between them. With the all-state model, we show that the V$_\text{O}$ defects play important roles in causing NBTI, which challenges the recent studies that discarded V$_\text{O}$ as a possible hole trap in NBTI. Our systematical calculations on the diversified V$_\text{O}$ properties and the all-state model provide the microscopic foundation for describing the reliability physics of MOSFETs and other transistors accurately.

cond-mat.mtrl-sci↗

arXiv2022

DASP: Defect and Dopant ab-initio Simulation Package

In order to perform automated calculations of defect and dopant properties in semiconductors and insulators, we developed a software package, Defect and Dopant ab-initio Simulation Package (DASP), which is composed of four modules for calculating: (i) elemental chemical potentials, (ii) defect (dopant) formation energies and transition energy levels, (iii) defect and carrier densities and (iv) carrier dynamics properties of high-density defects. DASP uses the materials genome database for quick determination of competing secondary phases and calculation of the energy above convex hull when calculating the elemental chemical potential that stabilizes compound semiconductors, so it can perform high-throughput prediction of thermodynamic stability of multinary compounds. DASP calls the ab-initio softwares to perform the total energy, structural relaxation and electronic structure calculations of the defect supercells with different structure configurations and charge states, based on which the defect formation energies and transition energy levels are calculated and the corrections for electrostatic potential alignment and image charge interaction can be included. Then DASP can calculate the equilibrium densities of defects and electron and hole carriers as well as the Fermi level in semiconductors under different chemical potential conditions and different growth/working temperature. For high-density defects, DASP can calculate the carrier dynamics properties such as the photoluminescence (PL) spectrum, defect-related radiative and non-radiative carrier capture cross sections, and recombination lifetime of non-equilibrium carriers.

cond-mat.mtrl-sci↗