We systematically investigated the optimum growth condition of wide-bandgap quaternary InAlGaN for ultraviolet (UV) light-emitting diodes (LEDs) grown on SiC by metal organic vapor phase epitaxy (MOVPE). We obtained intense UV emission in the wavelength of 315-370 nm from quaternary InAlGaN, which was as high as blue emission from InGaN. We found that the optimized growth temperature of quaternary InAlGaN is shifted from 790 to 870 °C as the emission peak wavelength is changed from 370-315 nm. The strongest PL was obtained with the wavelength around 330 nm. The growth condition for intense PL is found to be decided by two factors, i.e., the carrier confinement in In segregation region and crystalline quality. We also found that the small In mole fraction of 2-5 % is enough to obtain maximally PL intensity for InAlGaN, which is much smaller value than that for InGaN, due to the large carrier confinement with small In fluctuation.