Deep Levels and Electron Paramagnetic Resonance Parameters of Substitutional Nitrogen in Silicon from First Principles

Abstract

Nitrogen is commonly implanted in silicon to suppress the diffusion of self-interstitials and the formation of voids through the creation of nitrogen–vacancy complexes and nitrogen–nitrogen pairs. Yet, identifying a specific N-related defect via spectroscopic means has proven to be non-trivial. Activation energies obtained from deep-level transient spectroscopy are often assigned to a subset of possible defects that include non-equivalent atomic structures, such as the substitutional nitrogen and the nitrogen–vacancy complex. Paramagnetic N-related defects were the object of several electron paramagnetic spectroscopy investigations which assigned the so-called SL5 signal to the presence of substitutional nitrogen (NSi). Nevertheless, its behaviour at finite temperatures has been imprecisely linked to the metastability of the NSi center. In this work, we build upon the robust identification of the SL5 signature and we establish a theoretical picture of the substitutional nitrogen. Through an understanding of its symmetry-breaking mechanism, we provide a model of its fundamental physical properties (e.g., its energy landscape) based on ab initio calculations. Moreover by including more refined density functional theory-based approaches, we calculate EPR parameters (↔g and ↔A tensors), elucidating the debate on the metastability of NSi. Finally, by computing thermodynamic charge transition levels within the GW method, we present reference values for the donor and acceptor levels of NSi.

Nitrogen-Related Defects in Crystalline Silicon

“…EPR studies have determined that the off-center substitutional N is more stable than the on-center substitutional N [36,[58][59][60]. Interestingly, an argument for a metastable on-center configuration was put forward in order to explain the hyperfine splitting observed in the EPR spectra with increased temperature, and a symmetry breaking mechanism T d → C 3v was proposed [32,60]. An infrared band at explain the hyperfine splitting observed in the EPR spectra with increased temperature and a symmetry breaking mechanism Td → C3v was proposed [32,60].…”

“…Interestingly, an argument for a metastable on-center configuration was put forward in order to explain the hyperfine splitting observed in the EPR spectra with increased temperature, and a symmetry breaking mechanism T d → C 3v was proposed [32,60]. An infrared band at explain the hyperfine splitting observed in the EPR spectra with increased temperature and a symmetry breaking mechanism Td → C3v was proposed [32,60]. An infrared band a 653 cm −1 (at 300 K) was ascribed [61] to the N's substitutional impurity.…”

“…Thus, these complexes have been studied systematically both experimentally and theoretically. Experimentally, there have been a variety of techniques employed to study defects in semiconductors and, especially in this work, N-related defects in Si: a) those studying the electrical properties of defects [32][33][34][35] use, for instance, the deep-level transient spectroscopy (DLTS) technique which basically investigates the properties of deep levels in the forbidden gap of semiconductors; b) those studying the magnetic properties of defects [32,[36][37][38] use, for instance, the electron paramagnetic resonance technique (EPR) spectroscopy which is used to identify the electronic structure of defects and their charge states; and c) those studying the optical properties of defects use, for instance, infrared spectroscopy (IR) which mainly investigates using infrared absorption of the localized vibrational modes (LVMs) of the defects [39][40][41][42][43], as well as photoluminescence (PL) where light separates charge carries within the band or impurity structure of a semiconductor, and whose later recombination produce characteristic emissions [44][45][46].…”

Electron Spin–Lattice Relaxation of Substitutional Nitrogen in Silicon: The Role of Disorder and Motional Effects

“…The N Si center, termed SL5, has also been largely investigated in the past because of its unusual nature among the family of silicon donors. Its ground state is characterized by an [111] off-center configuration, which implies the presence of dynamical reorientations at room temperature [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Electron paramagnetic resonance (EPR) is naturally suited for the investigation of N Si due to its paramagnetic ground state; furthermore, it can follow the center thermal evolution due to the time scale of EPR experiments.…”