Yes, but it would suck or be really expensive.
TO back this up, the only f/1.8 lens I am aware of at wider than 24mm is the 20mm f/1.8 that Sigma has, and the reviews lean towards the "suck" side of things. And that's not a zoom and not going to 14mm. Seeing how insanely large the element is at 14mm f/2.8 on the Nikon zoom, I'd shutter to think what it'd be at f/1.8
Shallow DOF helps isolate the subject, no matter the focal length. I notice a big difference between f1.8 and f2.8 @ 50mm. I imagine such a difference would exist also at 15mm.
Except at 50mm, your focus plane is maybe a foot wide at f/1.8, so, you can isolate an object fairly easily. At 15mm, your plane is now 10ft in length, so trying to isolate that same object would fail. The background would have to be 10x as far away to get a similar effect.
I'm guessing you haven't shot ultra-wide; the reality is that even at f/2.8 on anything wide than 20mm, you can pretty much set focus about 1/3 to 1/2 way into a scene and get everything in focus. Not much isolation to be had in the ultra-wide realm without T/S