I'm interested in trying to find any research that compares (or can be used to compare) STEM students that go from undergrad straight to a PhD program vs those that get a Masters degree before getting accepted into a PhD program. Two possible aspects of this would be are there population differences between those that go on to a masters vs those that go to a PhD (such as if the undergrad university plays a large role in this) and how students that have already completed a masters degree do when they then go on to a full PhD program.

As education papers are out of my normal area of focus, I've been having a bit of trouble with finding where to start on this. Either with individual papers, or with what particular journals focus on this sort of thing.