GaN-based LEDs are technologically important because of their applications, such as display, signage, solid-state lighting and automotive headlight. To realize such applications, the enhancement of output power and low turn-on voltage of LEDs is essential. In this talk, we present ways of enhancing current injection efficiency through the formation of transparent and reflective ohmic electrodes. Various design rules are suggested to enhance current injection efficiency, such as the control of surface Fermi-level through surface etching, barrier tunneling, the modification of Schottky barrier heights (SBHs) by introducing nano-structures at the contact/GaN interface, control of native defects in GaN surface regions. On the basis of X-ray photoemission spectroscopy (XPS), Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM), and X-ray diffraction results, the ohmic formation and electrical degradation mechanisms are described and discussed. In addition, works on non-polar/semi-polar GaN are also presented.