PHYSICAL AND TECHNOLOGICAL ASPECTS OF THE METHOD OF NEUTRON TRANSMUTATION DOPING OF SEMICONDUCTORS AND PROSPECTS OF ITS APPLICATION IN UKRAINE

Neutron transmutation doping (NTD) is a state-of-the-art alternative to traditional doping methods, such as thermal diffusion and ion implantation. Traditional methods have restrictions, in particular, a problem of uneven distribution of impurities along the ingot due a high segregation coefficient. NTD overcomes these drawbacks ensuring uniform formation of impurity throughout the entire volume. Physical basis of the method is the absorption of thermal neutrons with 30Si nuclei, which leads to creation of intermediate radioactive isotope 31Si. Then this isotope decays, turning into stable doping element-phosphorus (31P). The probability of this process is characterized by the reaction cutoff cross-section which is the biggest for the thermal neutrons. Modeling of isotope accumulation kinetics shows that phosphorus concentration increases linearly with irradiation time allowing precise control of the doping level.