## 4 Progress in the Understanding of Illuminated B-O LID Mitigation Processes
### Role of Defect Formation  
In addition to providing a manipulation of hydrogen charge states to enable defect passivation, illumination also plays a critical role in accelerating the formation of defects, simply because a fast passivation process requires defects to form in the first place. On the one hand, a quadratic dependence of the defect formation rate on the equilibrium hole concentration (p\({}_{0}\)) was observed [24; 27; 28; 94; 128]. On the other hand, a dependence of the defect formation rate on the illumination intensity was also observed for low illumination intensities, up to approximately 0.01 suns, at which the reaction rate saturated [8; 129]. This illumination intensity corresponds to a saturation of the electron dependence for the reaction with an excess electron concentration on the order of 1 \(\times\) 10\({}^{11}\) cm\({}^{-3}\)[130]. Above such excess electron concentrations, the reaction rate in p-type silicon is determined by the background boron-doping concentration, typically on the order of 1 \(\times\) 10\({}^{16}\) cm\({}^{-3}\). However, [PERSON] et al. demonstrated that this fundamental limit of the defect formation rate imposed by the background doping concentration could be overcome by driving the silicon into high-injection conditions using high-intensity laser illumination [131]. It was proposed that the increased reaction rate with high-intensity illumination could be due to a dependence of the reaction rate on the total hole concentration, rather than the equilibrium hole concentration. This hypothesis has subsequently been confirmed by multiple authors [132; 133]. This breakthrough enabled full defect formation within four seconds, compared to typical defect formation processes requiring minutes to hours at temperatures below 200 \({}^{\circ}\)C using low-intensity illumination (in the order of \(\sim\)1-sun equivalent illumination) [134].  
The defect formation rate has important implications for the ability to eliminate B-O related LID [88, 89]. In particular, for conventional low-temperature processes, the defect formation rate is typically slower than that for passivation, hence resulting in a decay and subsequent recovery of lifetime during regeneration processes. Therefore, the ability to passivate B-O defects is limited by the availability of the defects for passivation [89]. Increasing the defect formation rate is therefore critical to accelerating the process of LID mitigation. Increasing the defect formation rate at a given temperature also increases the effectiveness of LID mitigation during illuminated annealing processes (the ratio of passivated to inactive defects). Higher defect formation rates enable the use of higher processing temperatures without sacrificing the effectiveness of LID mitigation [89, 93]. The increased temperatures can lead to a further acceleration of the processes due to the exponential dependence of the reaction rates on processing temperature as well as the increase in carrier concentrations and lifetime at higher temperatures [133, 135]. However, if an excessively high temperature is used, an incomplete regeneration will result [87]. Subsequently, the temperature is carefully chosen based on the illumination intensity used and typically in the range of 200-300 \({}^{\circ}\)C.