# Nitrogen-Related Defects in Crystalline Silicon
## 1 Introduction  
Si has been a dominant material in the semiconductor industry for over six decades. It has a wide range of applications in electronic, microelectronic, and optoelectronic fields and especially for nanoelectronic, nuclear medicine, and sensor and photovoltaic devices [1; 2; 3; 4; 5]. Typically, Si-based devices are fabricated on single-crystal Czochralski Si wafers. Importantly, all semiconductors contain defects, mostly impurities and lattice defects, which are introduced either during crystal growth and material processing or on purpose and by design for certain applications. The performance of Si-based devices is directly related to the properties of the defects present in the lattice. The technological necessity to improve the quality of Si to sustain and enhance the device efficiency depends on the control of the defects present in the lattice [6; 7; 8]. N is one of the fundamental impurities incorporated in the Si lattice and has attracted a lot of attention in the last 50 years [9; 10; 11; 12; 13; 14]. It is introduced in Si either during material processing in a nitrogen atmosphere or through implantation [9]. There is intensive research on the impact of N in Si, since it affects the properties of the material in many ways. It has been found that N introduction into Si enhances the mechanical strength of the wafers, thus obstructing the movement of dislocations during thermal treatments [15; 11; 16]. It also enhances oxygen precipitation, which is important for internal gettering as it suppresses the effect of deleterious metal contaminants [13; 17]. It also suppresses self-interstitial diffusion and controls the density and size of crystal-originated particles (COPs) [11; 12; 13; 18], thus improving dramatically the gate oxide integrality of semiconductor devices. It suppresses void formations, which are essentially vacancy aggregates that degrade properties of the devices [12; 19]. This is directly correlated with the formation of nitrogen-vacancy pairs [20]. N suppress interstitial- (A-swirl) and vacancy (D-voids)-related defects [12; 21]. Generally, diffusion and/or the aggregation process of Si self-interstitials and vacancies are affected by N incorporation [22]. The N-suppression effect on the as-grown defects in Si is very suitable for the fabrication of insulated gate bipolar transistors (IGBTs) which have attracted considerable attention for their potential use in the electric vehicle industry [23]. There is experimental evidence that N implantation in Si induces transient enhanced diffusion of dopants [24]. N can suppress the effect of deleterious defects in Si, for instance of substitutional Au impurities, by reducing their concentration [25]. It has been determined that the pulling rate range of defect-free crystal is wider in N-doped Cz-Si, which is a key issue in Si technology [26]. It has also been reported that N incorporation in Cz-Si has no significant effect on the denuded zone of the crystal which can satisfy the requirements of the microelectronic industry [27]. Importantly, N in Cz-Si reduces high-purity-argon consumption during processing which in turn reduces the cost of Si crystal growth [13]. N incorporation in the Si lattice is, therefore, very important for the improvement of the efficiency of Si-based devices for certain applications. One key issue is the ability of N to form complexes with vacancies as well as with other impurities such as oxygen and carbon. Density functional theory (DFT) calculations have shown that the formation of such complexes is energetically favored [22; 28; 29]. The interaction of N with the above defects can lead to complexes, some of which are electrically inactive [30], and others are active, such as for instance shallow thermal donors [31]. Apparently, a better understanding of the physical properties of these N-related complexes will improve the quality of Si wafers and thus enhance the efficiency of the devices. Thus, these complexes have been studied systematically both experimentally and theoretically.