An Atomistically Informed Device Engineering (AIDE) Method Realized: A case study in GaAs

TL;DR

The paper introduces the Atomically Informed Device Engineering (AIDE) method, integrating first-principles defect data with experimental inputs in the REOS continuum device code to model dynamical defect evolution under irradiation. Using Si-doped GaAs as a case study, it demonstrates (i) movement and convergence of quasi-Fermi levels, (ii) charge-equilibration dynamics verified by defect charge-state populations, and (iii) a diffusion-driven, Coulomb-assisted reaction forming a GaAs defect complex. The results show how the Fermi level position constrains defect populations and enables rare, short-time defect interactions to be studied virtually. The approach offers a general framework to bound difficult-to-measure physical quantities, extendable to other materials like InGaAs, and provides insight into defect annealing and long-term device reliability in radiation environments.

Abstract

Radiation-induced defects can have a significant impact on the longevity and performance of semiconductor devices. We present an Atomistically Informed Device Engineering (AIDE) method that integrates first-principles defect properties and experimentally measured parameters into a device model to dynamically simulate the defect chemistry in semiconductors. For a silicon-doped gallium arsenide (GaAs) material, we showcase three capabilities: (i) Fermi level $E_F$ movement including its component electron and hole Fermi levels, (ii) dynamical charge equilibration with the arsenic vacancy serving as an example, and a (iii) diffusion-driven reaction between Coulomb attracted gallium interstitial ($Ga_i$) and arsenic vacancy ($v_{As}$). Governed by charge carrier reactions, the electron and hole Fermi levels remained dissimilar until equilibrium was achieved at $E_F\approx1.32$ eV. The equilibrium Fermi level was verified by successfully identifying $v_{As}^{3-}$ as the most populated charge state within the arsenic vacancy defect. Lastly, a Coulomb attraction, created by the shifted Fermi level and the charge equilibration process, between $Ga_i^{1+}$ and $v_{As}^{3-}$ resulted in the formation of a doubly negative gallium antisite ($Ga_{As}^{2-}$). The AIDE method can access experimentally inaccessible short-time and low-concentration regimes, is generalizable to other more complex systems (e.g., indium gallium arsenide), and, after solving open problems in GaAs, will serve as a virtual experiment to bound estimates for difficult-to-measure physical quantities.

Figures (7)

• Figure 1: Illustrative representation of the electron irradiation process and the sequential steps involved. The representation starts with the electron entering the material, causing the generation of defects, and ends when the system reaches a new steady-state equilibrium.
• Figure 2: Illustrative representation of the Atomically Informed Device Engineering (AIDE) method and its inclusion in the REOS device software suite. The experimental (EXP) defect properties includes illustrations of a DLTS spectra and a mapping of the peaks onto the GaAs bandgap. The DFT defect properties include a defect level diagram extracted from schultz2009 and a illustrative representation of the migration barrier.
• Figure 3: Qualitative defect level diagram for a generic defect $a$ in three different charge states (-1, 0, and +1) and two transition levels. Red arrows indicate how charge flows via charge carrier capture and emission reactions.
• Figure 4: First-principles computed defect levels of $v_{As}$, $Ga_i$, and $Ga_{As}$ in irradiated Si-doped GaAs schultz2009schultz2016. The brackets indicate -U behavior.
• Figure 5: REOS computed Fermi level for the $e^-$ and $h^+$ in GaAs. Equilibrium is achieved in roughly 1 s where the Fermi level for the charge carriers reconcile at $E_F\approx1.32$ eV.