High-power light-emitting diodes (LEDs) have been fabricated through multi-chip integration of small near-ultraviolet (n-UV) LED chips by using a direct flip-chip bonding technique. Based on optical measurements, the absorption of light between adjoining LED chips was not observed when temperature was held constant, although the luminescence characteristics of the LED decreased with increasing package temperature. Large-scale integration LEDs (LSILEDs) with radiant fluxes over 2 W and 121 LED chips in a single package were fabricated. Four types of packages with different chip densities revealed the importance of thermal management through the control of the number and density of the LED chips in order to obtain high radiant flux and high efficiency.