Measurements of ^{3 1}P Concentrations Produced by Neutron Transmutation Doping of Silicon

Abstract

The absolute concentrations of ^{3 1}P, produced by the irradiations of float zone silicon samples in the Texas A§M University Research Reactor, have been measured to an accuracy of ± 10%. The neutron fluence was varied from 10¹⁶ to 10¹⁸n/cm², which corresponded to ^{3 1}P concentrations in the 10¹² to 10¹⁴ atoms/cm³ range. The results are based on measurements of the absolute activities of ^{3 1}Si by detection of 1.266 MeV gamma rays. Secondary standards of Fe were required for the larger neutron fluences. The ^{3 l}p concentrations were compared to the concentrations of electrically active P following 850°C anneals for 1 hour. These concentrations were determined in the same samples from temperature-dependent Hall effect measurements at Hughes Research Laboratories. The two results agree to within experimental error, thus confirming that transmuted P in the 10¹² to 10¹⁴ atoms/cm³ range is completely electrically active following 850°C, 1 hour anneals of float zone silicon. In addition, a corrected value for the gamma abundance of³¹Si was established to be 5.6 x 10^-4 ± 10%.