Realization of compact, low cost and highly efficient light sources in the deep-UV region would benefit a number of applications. Laser diodes with emission from 250 to 340 nm are a critical element that enables fluorescence-based biological agent detection. Incoherent sources (LEDs) would find applications in air and water purification, and also in fluorescence-based bio-detection. While a number of materials problems limit the performance of current device designs, the reduction of threading dislocations in the starting AlGaN epilayer has reliably resulted in higher device efficiency, power, and lifetime. In this work, Al<SUB>0.32</SUB>Ga<SUB>0.68</SUB>N templates were fabricated with a threading dislocation density (ρ) of 1-2 x10<SUP>8</SUP> cm<SUP>-2</SUP> uniformly distributed over large, wafer-size areas. We epitaxially grew Al<SUB>0.32</SUB>Ga<SUB>0.68</SUB>N over parallel trenches etched into previously prepared AlGaN(Si)/AlN/sapphire templates (ρ = 2-3x10<SUP>9</SUP> cm<SUP>-2</SUP>). Regions of high dislocation density (~ low 10<SUP>9</SUP> cm<SUP>-2</SUP>) over mesas and at the center of trenches  were eliminated by optimizing mesa width, period, and etch depth of the trench patterned into the starting AlGaN template. Unlike previous reports , the overgrown AlGaN layer is doped with Si (No ~ 2x10<SUP>17</SUP> cm<SUP>-3</SUP>), reducing the sheet resistance of front-side contacted devices and allowing for easier fabrication of vertically conducting emitters. Since dislocation densities are spatially uniform across the wafer, laser diodes can be processed without aligning to the underlying pattern and the entire device area of LEDs utilizes low dislocation material. Cathodoluminescence was used to measure the density and spatial distribution of threading dislocations in AlGaN epilayers grown over patterned AlGaN/AlN templates. Consistent with the low dislocation density results from cathodoluminescence, photoluminescence from GaN-AlGaN quantum wells (QWs) is 7x higher when grown on a patterned AlGaN template compared to QWs grown on an unpatterned AlGaN template. Similarly, on-wafer electroluminescence under low current injection (~ 13 A/cm<SUP>2</SUP>) is 12x higher for laser diode structures grown on patterned vs. unpatterned AlGaN templates. Finally, we have recently extended this approach to higher Al compositions exceeding 0.60, achieving a low 10<SUP>8</SUP> cm<SUP>-2</SUP> dislocation density at compositions suitable for solar-blind photodetectors and LEDs emitting at 280 nm. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.