Impact of Defects Formed in Neutron Transmutation Doping of Silicon on Device Performance

Abstract

Defects introduced into silicon material as a result of neutron transmutation doping (NTD) cover the entire range of level of complexity in which the defect inventory can include relatively simple point defects to large disordered regions of ≲500A size up to rod-like defects 10µm long 200A diameter. The wide spectrum of defect specie occurs since the dominant defect producer, the fast neutrons, can impart on the average ∿50keV of recoil energy to a silicon atom while recoiling silicon atoms subsequent to neutron capture and gamma radiation emission can have energies in the ∿400 to 900eV range. In this paper a review will be given on properties of defects introduced in silicon specific to NTD. The approach will be to describe the origin of defects and their effects on extrinsic photoconductivity, optical properties, transmission electron microscopy and electron spin resonance, including defect symmetry properties and the response and alteration of defects with heat treatment. A discussion is given on the nature of unannealable defect microstructure in NTD Si. An analysis of many experiments suggest that it may be advantageous to perform irradiation in NTD Si at temperatures of 500–600°C. Finally, an attempt will be made to show how the defects can effect the operation of devices, eg: high power thyristors, transistors, infrared detecting devices and very large scale integrated circuit systems.