In this study, HfO2 thin films were deposited onto the Si substrates by RF magnetron sputtering system. After deposition, the HfO2 thin films were then heated by a furnace thermal annealing process in air and at 400-700oC. The surface morphologies and crystalline characteristics of the HfO2 thin films were investigated by using SEM and XRD patterns. The grain sizes and crystalline phases increased with rising annealing temperature. In addition, the SiO2/HfO2 distributed bragg reflector (DBR) was used for improving the external quantum efficiency of the GaN-based LEDs. The output power of LEDs with 9-pair SiO2/HfO2 DBR and with Ag mirror+6-pair SiO2/HfO2 DBR were increased by approximately 10.6% and 7%, respectively, as compared with the LEDs without SiO2/HfO2 DBR.