We present an epitaxial overgrowth process for reducing threading dislocations in AlxGa1-xN over the entire compositional range. This process avoids the use of UV-absorbing GaN layers and results in a spatially uniform defect reduction which eliminates the need for precise alignment of devices to low-defect areas of the wafer. Using the described overgrowth process, we demonstrate Al0.3Ga0.7N and Al0.6Ga0.4N epilayers with a dislocation density of 2 x 10(8) cm(-2) and 5 x 10(8) cm(-2) respectively, rendering them suitable as templates for deep-UV bottom-emitting LEDs and laser diodes. The process involves patterning of submicron-wide-stripes, less than 1 mu m in height, into an AlGaN/AIN/sapphire template and subsequent regrowth of a 5-10 mu m thick AlGaN epilayer. The sub-micron width of the mesa allows for bending of threading dislocations that would continue to thread vertically through wider mesas. Utilizing 1.3 mm-thick sapphire substrates (3 x thicker than commonly used), epilayer cracking from regrowth is eliminated and wafer bow over a 2-in diameter substrate is reduced to less than 15 mu m. We observed a 7 x increase in photoluminescence intensity from GaN-AlGaN multi-quantum well structures emitting at 340 am and a 15 x increase in electroluminescence from laser diode heterostructures when grown on patterned Al0.3Ga0.7N templates. (C) 2013 Published by Elsevier B.V.