The Improvement of Bonding Metal Layers in a GaAs Vertical Structure Light-Emitting Diode Package

Abstract

This paper presents an investigation into the reliability of substrate bonding between metal layers and gallium arsenide vertical-injection light-emitting diodes (GaAs VLEDs). In this study, molybdenum (Mo) acts as a buffer layer between the GaAs VLED and the aluminum-based metal core printed circuit board (MCPCB). The thermal expansion coefficient (CTE) value of GaAs is approximately equal to that of the Mo layer under the substrate. This is beneficial for slowing the decay of the adhesive bond due to temperature cycling from − 40°C to 125°C for 50 cycles. The experimental results show that the use of the Mo buffer layer greatly improved the electrical and optical performance of the LED packages. The average leakage current was reduced from 33.63 mA to 2.37 mA at the reversed voltage of − 3 V and the increase in light output power was 130% at an injection current of 0.7 A. The results also show that a Mo buffer layer can reduce the risk of cracking on bonding wires after the thermal shock test (TST). These results are useful for improving the aging of GaAs VLEDs.