What is best low growing, full sun, dry soil, fast growing, perennial ground cover ?

I have a full sun, fairly dry slope l need to cover. I would prefer a low growing darp green foliage. The temps. in our area range from -20 F to 105 F. The soil is clay with a bit of humus from tree leaves. The area now has wild morning glory & a plethora of other types of weeds which fare quite well. l like the color of the leaves of the perewinkle & it's plant height, but don't know how it handles full day of sun.