Group III-nitride-based LEDs are of great technological importance because of their applications including display, solid-state lighting, automotive headlight, and water/air purification. For these applications, the attainment of high external quantum efficiency (EQE) of LEDs is essential. On the one hand, their applications necessitate the fabrication of different geometry LEDs, such as lateral-type, vertical-type, and flip-chip LEDs, which require different design rules of electrodes and current spreaders. To maximize the EQE, it is important to increase the light extraction efficiency (LEE). In addition, the improvement of current injection (by forming low contact resistivity) and current spreading is vital for the fabrication of high-efficiency LEDs. It is well known that lateral LEDs suffer from the light extraction limit due to the absorption of the metal contacts, such as n and p contacts, and bond pads. In addition, p-GaN has characteristic problems, which make it difficult to achieve device-quality ohmic contacts with the specific contact resistance lower than ~10^–4 Ωcm² because of the difficulty in growing a highly doped p-GaN and the absence of appropriate metals or conducting oxides having work function larger than that of p-GaN. Thus, for the formation of ohmic and reflective contacts to p-GaN, also serving as light extractor and/or current spreader, transparent conducting oxides (TCOs)-based and Ag-based schemes have been extensively investigated. In this talk, we present methods of enhancing current injection efficiency through the formation of transparent and reflective ohmic electrodes. Design rules are suggested to enhance current injection efficiency, such as the control of surface Fermi-level through surface treatment, barrier tunneling by forming interfaces with inhomogeneous Schottky barriers, the modification of Schottky barrier heights (SBHs), control of native defects in GaN surface regions. Furthermore, nanostructures, such as Ag nano-dots (NDs) and Ag nano-wires (NWs), are used to enhance the light output powers of GaN-based LEDs. Finally, on the basis of scanning transmission electron microscopy, X-ray photoemission spectroscopy, secondary ion mass spectroscopy and Auger electron spectroscopy results, possible ohmic formation and electrical degradation mechanisms are described and discussed.