Laser Induced Dynamics Of Impurity Atoms And Mechanisms Of Damage In Semiconductor Materials

Impurity has a decisive impact on semiconductor materials. Whatever the purposely active doping to satisfy a particular demand or the passive doping during its manufacturing process, the existence of dopant is one of the intrinsic properties of semiconductor materials or devices, which should be taken into seriously account. The subsequent local absorption, coupling, and impurity dynamics introduced from laser-induced impurity distribution can lead to the energy transport and electric field redistribution of incident laser, which makes an important or even decisive impact on the characteristics of semiconductor materials and the interactions between laser and semiconductor materials. However, the micro physical images and its influences on macro material properties caused by laser-induced impurity or defects distribution and dynamics evolution are still a lack of mature recognition, which is same for theoretical model description or the capability of prediction.In this thesis, we take Ti-doped single crystal silicon material as our object of research. Combing with quantum chemistry, classical rate theory and Monte Carlo method, we systematically studied the relationships between distribution, evolution and macro physical properties of the laser-induced defects dopant in semiconductor material. Fisrt, we began with the influence of laser parameters and initial defect status on dynamics process of dopant migration and the way of dopant intensifying the laser field. Further, the dynamics model of dopant distribution in laser-induced semiconductor materials based on First-principle and Monte Carlo method was introduced. Also, new thoughts of studying the micro physical processes and the relationships between macro physical properties of laser-induced semiconductor materials have been presented. The achievement details as follows:(1) Laser parameters, dissolution factor of materials and vacancy concentration have a great influence on defects dopant migration principles. The migration velosity of dopant get increased with the intensity of laser power, or with the decrease of dissolution factor of materials, of which tendency satisfies the double exponential decay with time. However, such relationships between dopant migration and vacancy defects concentration are intricate. In the condition of dense vacancy concentration, the maximum density of defects dopant atoms has a trend from rise to decline with the time duration of laser radiation. A relatively high vacancy concentration has benefit on the dissipation of defects dopant atom concentration, while such dissipation will be retarded when the vacancy concentration is exaggerated high.(2) Spatial distribution of laser-induced defects impurity atoms shows a relatively high ununiformity, with randomly appearring peaks or valleys in the concentration of defects impurity atoms. When the laser radiation durations get increased, locations of that peaks and valleys are stable to some extent, while the concentration peaks of defects impurity atoms are intensified, which means the augmentation of defects impurity with the prolonged duration of laser radiation, and the appearance of specific geometrical envelope of locally distributed impurity in material when local concentration increases.(3) With laser radiating, light field in silicon materials is subject to the configuration and concentration of locally distributed impurity, as well as the laser wavelength. As for a certain configuration of impurity's local distribution, those areas in which field get augmented are always on the edges of doping range. In the condition of multi-configurations of impurity distribution, especially for two impurity spheres with distinct size, the electric field augmentation in the vicinity of small one is stronger when the radius discrepancy of the two spheres is larger. Practically, this makes sense to the control of material damages via defects.(4) We confirmed experimentally that the outcome of absorption cross-section or light field intensification in Ti-doped silicon single crystal is derived from the absorption of defects impurity. When p-n junction is radiated, metal (electrode) in silicon surface will migrate or diffuse into the p-n junction, causing redistribution of impurities and subsequent local damage of the junction, which induce degradation of photoelectric properties. This can be regarded as a further validation for the purpose of this thesis:focusing on the deep understanding of mechanisms of laser-induced damage from the perspective of defects.In this article, we laid the foundations for exploring the origination of laser-induced damage mechanism of semiconductor materials, and the method which can be used to achieve and manipulations of material properties by using interactions between impurities in semiconductor materials and lasers. Meanwhile, a new way of achieving the predictions from micro physical process to macro invalidation of laser-induced materials, of exploring widely-spanned-scale calculations, is presented.