Using a micro-pixel design, we report the demonstration of high-power deep UV AlGaN-based light-emitting diodes (LEDs) with peak emission wavelength at 280 nm. The design comes in response to lateral current crowding problems, which severely limit the maximum possible active area and the overall performance of ordinary square geometry III-nitride LEDs fabricated on insulating substrates. It is shown that the interconnected micro-pixel geometry significantly reduces both the device series resistance and the thermal impedance, thereby improving heat dissipation and increasing the maximum optical power. The design imparts ever-increasing advantages as the operating wavelength decreases (and the aluminum content increases). The optical power of the 10×10 pixel array with an effective area of 222×222 μm2 only saturates at dc currents higher than 200 mA, which is nearly 50% greater than found for a square geometry LED with identical junction area, fabricated from the same wafer. These 280 nm LEDs demonstrated a high on-wafer cw power of 145 μW with 200 mA of pumping current.