First principles simulations of microscopic mechanisms responsible of the drastic reduction of electrical deactivation defects in Se hyperdoped silicon

By first principles simulations we systematically investigate Se hyperdoped silicon by computing, for different types of Se complexes, the formation energy as a function of dopant concentration.We identify the microscopic mechanisms responsible of the dramatic reduction of electrical deactivation defects as the number of dopant concentration approaches the critical value, xc, at which the insulator-to-metal transition occurs. We discuss the electrical properties of Se point defects and Se complexes, enlightening the formation and the nature of the impurity band in the bandgapand how the presence of different type of complexes may increase the broadening of the impurity band and affects the insulator-to-metal transition. We individuate the best doping range in which the properties of the impurity band can be engineered according to the needs of electronic industry.Simulations of the structural properties of the complexes complete the work.Our findings are relevant for intermediate impurity band applications.