Engineering the insulator-to-metal transition by tuning the population of dopant defects: first principles simulations of Se hyperdoped Si

Chalcogens are extremely promising to hyperdope Si because of their superior electronic properties with respect to group V elements of periodic table traditionally employed as dopants. Within the framework of plane wave pseudopotential techniques we computed the formation energy of different types of defects formed by dopants in Se hyperdoped Si, as a function of the dopant concentration. Moreover, we studied the possibility to tailor the electronic properties of the system, by tuning the probability that each type of defect could form. In particular, by using supercells exceeding the thousand of atoms we characterized the double impurity band structure of Se3-VSi complex formed by a Si vacancy surrounded by three Se, that presents a shallow metallic impurity band and a deep insulating impurity band in Si bandgap, thus allowing sub-threshold photon absorption, and suggesting that a significantly improvement of the performance of Se hyperdoped Si as infrared detector, can be achieved by increasing the population of Se3-VSi complexes. Our findings relate the range of microscopic size in which the dopants can diffuse to the population of different types of complexes, revealing the possibility of engineering the critical concentration at which the Insulator-to-Metal transition occurs by varying the diffusion length of dopant. Our results pave the way to the exploitation of Se hyperdoped Si as building block in new conception ultra-scaled nano-electronic devices, infra-red detectors, and intermediate band photovoltaic applications