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

Abstract

Chalcogens are extremely promising for hyperdoping Si because of their superior electronic properties with respect to group V elements of the 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 of tailoring the electronic properties of the system, by tuning the probability that each type of defect can form. In particular, by using supercells exceeding thousands of atoms we characterized the double impurity band (IB) structure of complex, formed by a Si vacancy surrounded by three Se, which presents a shallow metallic IB and a deep insulating IB in the Si band gap, thus allowing sub-threshold photon absorption, and suggesting that a significant improvement in the performance of Se-hyperdoped Si as an infrared detector, can be achieved by increasing the population of complexes. Our findings relate the range of microscopic sizes in which 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 the dopant. These results pave the way for the exploitation of Se-hyperdoped Si as a building block in newly conceived ultra-scaled nano-electronic devices, infra-red detectors and intermediate-band photovoltaic applications.