  It is surprising that only an enhanced low-dose-rate sensitivity (ELDRS), but
not its contrariety, a reduced low-dose-rate sensitivity (RLDRS), is
experimentally observed in bipolar junction transistors. In this work, we
attribute this strong asymmetry to an overwhelming superiority of hydrogen
cracking reactions relative to Shockley-Read-Hall recombinations. We
demonstrate that this situation can be completely reversed and an RLDRS effect
can occur by decreasing the concentration ratio between hydrogen and
recombination centers. We show that the decrease of recombination rate of holes
(generation rate of protons) with increasing dose rate is responsible for the
positive (negative) dose-rate dependence of RLDRS (ELDRS). We also find an
RLDRS-ELDRS transition for decreasing dose rate, in which the transition point
can be controlled by the concentration ratio. The proposed RLDRS effect and its
tunability pave a way for a credible acceleration test of the total ionizing
dose damage in different low dose rate environments.
