Stable-Damage Comparisons for Neutron-Irradiated Silicon

Measurements of minority-carrier lifetime degradation have been made for neutron-irradiated silicon which permit the following stable-damage comparisons to be drawn: a) test vehicle (device vs. bulk material); b) material type (n-type vs. p-type); c) dopant density (data obtained for various resistivities); d) neutron energy (14-MeV vs. reactor); e) measurement technique (transient vs. steady-state); f) operating condition (data obtained over a wide injection-level range). Primary results of this study are the following: a) the 14-MeV-to-reactor stable damage ratio is insensitive to injection level for a given resistivity; b) measurements of the stable damage ratio were made for bulk silicon and solar cells of various resistivities and nearly all of the values obtained were in the range 2.3 ± 0.4; c) neutron damage constants for solar cells and bulk material of a particular resistivity are in reasonable agreement if comparison is made at the same injection ratio, provided that the ratio employed is high enough so that such comparisons are not affected by bulk trapping.