Abstract
Nitrogen-vacancy defects are important for the material properties of silicon and for the performance of silicon-based devices. Here, we employ spin polarized density functional theory to calculate the minimum energy structures of the vacancy-nitrogen substitutional, vacancy-dinitrogen substitutionals, and divacancy-dinitrogen substitutionals. The present simulation technique enabled us to gain insight into the defect structures and charge distribution around the doped N atom and the nearest neighboring Si atoms. Using the dipole–dipole interaction method, we predict the local vibration mode frequencies of the defects and discuss the results with the available experimental data.
Highlights
Defects are present in silicon mainly because of crystal growth and processing conditions.[1,2] These can impact the material properties of silicon and the performance of devices
We focus on nitrogen (N), which is important for processing devices, as it can lock dislocations and increase the mechanical strength of wafers.[3]. This is significant for the very large scale integration (VLSI) and ultra-large-scale integration (ULSI) technologies of Si as it permits the Si wafer to undergo a range of processing steps without breaking
In order to validate the quality of the basis sets and pseudopotentials used in this study, we performed a series of single point calculations on the crystal structure of cubic Si26 as shown in Fig. 1(a) to obtain the equilibrium lattice constants and bulk modulus
Summary
Defects are present in silicon mainly because of crystal growth and processing conditions.[1,2] These can impact the material properties of silicon and the performance of devices. The introduction of N results in larger wafers with improved mechanical stability and wafer flatness. The positive impact of N includes the suppression of the negative effect of metal contaminants[4] and the reduction in voids and microdefects (for example, A-swirls and D-defects) during float-zone crystal growth.[5,6] Importantly, the interaction of N with oxygen-related defects affects the formation of thermal donors in Si, influencing the electrical properties of Czochralski grown Si.[7] It is beneficial as it prevents the formation of A-centers[8] and enhances oxygen precipitate formation.[9] To summarize, N influences the mechanical, optical, and electrical properties of Si.[10].
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