Radiation measurements after irradiation of silicon for neutron transmutation doping

Neutron transmutation doping of semiconductors is an important method for applications that require high dopant homogeneity. For silicon, it is based on the conversion of Si-30 into P-31 through a Si-30 (n,gamma) Si-31 reaction during neutron irradiation following beta decay of Si-31 to P-31. Neutron irradiation is usually performed in research reactors. The main characteristics of a doped silicon sample are (1) purity of the original silicon, (2) average phosphorus concentration and (3) phosphorus concentration homogeneity (uniformity). This paper describes measurement methods that utilise radiation induced during doping irradiation to measure these characteristics. The first two parameters can be measured using gamma spectrometry. The main part of the paper deals with homogeneity measurement. It describes a measurement method that is based on the detection of beta radiation from Si-31. Examples of experimental results are given. The experiments were performed in the LVR-15 research reactor. (C) 2013 Elsevier Ltd. All rights reserved.