Formation of High-Quality Ag-Based Ohmic Contact to p-Type GaN for UV LEDs Using a Tin-Zinc Oxide Interlayer

We report on the formation of high-quality ohmic contacts to p-GaN for UV flip-chip light-emitting diodes (LEDs) using a tin-zinc oxide (TZO) interlayer. It is shown that the TZO contacts produce contact resistivity of and reflectance of 76% at when annealed at . Near-UV LEDs made with the annealed TZO/Ag p-contacts give forward-bias voltage of at , and higher output power than those with single Ag contacts. Based on transmission electron microscopy and electrical results, possible ohmic formation mechanisms are discussed.