Improved light output power of GaN-based light-emitting diodes by using Ag grids

Abstract

We investigate the effect of 1-(1-D) and 2-dimensional (2-D) patterned Ag grids combined with Al-doped ZnO contacts on the electrical and optical properties of GaN-based light-emitting diodes (LEDs). The ratio of the grid width to the gap between the grids varies from 2.8 for the 1-D to 38.7 for the 2-D grids. All of the patterned Ag grid/AZO contacts show transmittances in the range of 86.4-94.0%. The LEDs fabricated with the differently patterned Ag grid/AZO contacts exhibit forward-bias voltages ranging from 3.67 to 4.62 V at an injection current of 20 mA, which are much lower than those (7.44 V) of the LEDs with the AZO only contacts. It is further shown that the LEDs with the patterned Ag grid/AZO contacts produce a 78.0-108.7% higher output power (at 20 mA) than those with the AZO only contacts. The reason for the improved output performance of the LEDs with the Ag grid/AZO contacts is briefly described in terms of the contact areas and plasma-induced damage of p-GaN. (C) 2012 Elsevier B.V. All rights reserved.