Simulation of Single Particle Displacement Damage in Silicon–Part II: Generation and Long-Time Relaxation of Damage Structure

Abstract

A statistical study of displacement cascades induced by silicon Primary Knock-on Atoms (PKA) in bulk silicon is performed by running a large number of molecular dynamics (MD) simulations. The choice of the PKA species and energy varying from 1 to 100 keV comes from a previous particle-matter simulation [1]. The electronic stopping power missing in standard MD simulations is here taken into account using the Two Temperature Model (TTM). This prevents from overestimating the number of created defects. The damaged atomic structures obtained after one nanosecond of MD simulation are not representative of what is observed in image sensors for example after several minutes. For this reason, the kinetic Activation Relaxation Technique (k-ART) is used in a second step, allowing to access longer simulation times of up to second. The obtained damaged structures can then be compared with experimental observations. Analysis reveals two possible links between the simulated structures and the measurements in solid-state image sensors. First, the cluster size distribution exhibits a shape similar to the measured exponential distribution of Dark Current (DC). Second, the temporal evolution of metastable atomic configurations resembles experimental DC-Random-Telegraph-Signals.

Simulation of Single-Particle Displacement Damage in Silicon—Part III: First Principle Characterization of Defect Properties

“…To tackle this question, a novel simulation approach has been developed (see [1] and [2]) based on the one proposed in [3]. It combines several simulation steps using different methods linked one to another as shown in in [1] and [2].…”

“…To tackle this question, a novel simulation approach has been developed (see [1] and [2]) based on the one proposed in [3]. It combines several simulation steps using different methods linked one to another as shown in in [1] and [2]. As detailed in [1], the main advantages of this methodology are the following: simulations start from realistic PKA (Primary Knock-on Atom) energies; large statistics of possible PKA directions are simulated, thus resulting in a statistically meaningful library of generated defect configurations; the electronic stopping power is taken into account; simulation times on the order of one second are reached, which gives access to direct comparison with experimental data.…”

“…As detailed in [1], the main advantages of this methodology are the following: simulations start from realistic PKA (Primary Knock-on Atom) energies; large statistics of possible PKA directions are simulated, thus resulting in a statistically meaningful library of generated defect configurations; the electronic stopping power is taken into account; simulation times on the order of one second are reached, which gives access to direct comparison with experimental data. This last crucial point has been obtained by using a KMC method called the kinetic Activation Relaxation Technique (k-ART) [2]. This method, by overtaking the timescale limit of classical MD simulations, offers the possibility of relaxing a large library of defects and defect clusters over 1s after the initial interaction as demonstrated in [2].The access to this long time scale has enabled to draw some first important conclusions regarding the origin of the radiation induced Dark Current (DC) and Dark Current-Random Telegraph Signal (DC-RTS) measured in image sensors as discussed in [2]:…”

“…This last crucial point has been obtained by using a KMC method called the kinetic Activation Relaxation Technique (k-ART) [2]. This method, by overtaking the timescale limit of classical MD simulations, offers the possibility of relaxing a large library of defects and defect clusters over 1s after the initial interaction as demonstrated in [2].The access to this long time scale has enabled to draw some first important conclusions regarding the origin of the radiation induced Dark Current (DC) and Dark Current-Random Telegraph Signal (DC-RTS) measured in image sensors as discussed in [2]:…”

“…This work is particularly focused on two defect configurations; the di-vacancy and the triinterstitial, both identified in previous Molecular Dynamics (MD) and kinetic Activation Relaxation Technique (k-ART) simulations [1,2]. By combining structural, energy and migration properties evaluated within the framework of the standard Density Functional Theory (DFT) and electronic properties calculated within the G 0 W 0 approximation, a reconstruction of the corresponding thermallyactivated electrical signal generated by each defect is obtained.…”