Silver-induced activation for improving the electrical characteristics of GaN-based vertical light-emitting diodes

Abstract

Silver (Ag) contacts are important reflectors for vertical-structure GaN-based light-emitting diodes (LEDs). The Ag contacts produce good electrical and optical properties at different annealing temperatures. Thus, in order to best optimize the reliability of LEDs, we introduced an Ag activation process before performing normal annealing treatments. In other words, after removing 200-nm-thick Ag layers on p-GaN that were annealed at 500 degrees C for 1 min, Ag films were deposited on the Ag-activated p-GaN, which were subsequently annealed at 300 degrees C for 1 min. The activated LEDs fabricated with the 300 degrees C-annealed Ag contacts reveal better electrical properties than the reference LEDs. For example, the activated LEDs give a forward voltage of 2.92 V at an injection current of 20 mA, whereas the reference LEDs with the 300- and 500 degrees C-annealed Ag contacts yield 3.02 and 2.98 V at 20 mA, respectively. The activated LEDs yield 4.9% and 17% higher output power (at 30 mW) than the reference LEDs with the Ag contacts annealed at 300 and 500 degrees C. The activation-induced electrical improvement is briefly described and discussed. (C) 2012 Elsevier B.V. All rights reserved.