Search for people ... "contains" vs. "is"

When I enter a part of a name in the Search-Field i get several results - so obviously this is a "contains" search that is performed throughout the Username and the real name.

But in the search for people in the sidebar-module it seems to be a search for "equal to" and only in the Username. How can I change this to a "contains" search similar to the one above as well?

Thanks for your help