This Gray's artical is the best one to help you learn the effect of doublet,You can also
read "the gain-boosted technology",it can been taken as a practical example of doublet.
This is the paper with the topic "Relationship between Frequency response and settling time of operational amplifies",
But I can't find the "gain-boosted technology" special documentation.
if you mean pole zero doublet ; it results in 2 time constants , one normalized to their sum and other to their difference , and so if you use fourier , you will show that in time , they add such that the signal rises very sharp and settles in a very big time , in opamps i think they use pole zero tracking to avoid it ; see gray & meyer book or ken martin one