Yes you are right, some styles of music in minor keys have the 5th chord as Dominant 7th chord, rather than a minor chord. A big part of the reason for this is to create musical tension with a more satisfying release.

for example, in this chord progression:

Aminor7b5//D7//Gminor

The D7 to the Gminor sounds really satisfying compared to say Dminor to Gminor.
The G harmonic minor is of course a good scale to play over this progression, as is the melodic minor ascending.

I could go into greater detail but it would be confusing....