Investigation of Cr- and Al-based metals for the reflector and Ohmic contact on n-GaN in GaN flip-chip light-emitting diodes

Abstract

This letter investigates three composite metals used as a reflector and Ohmic contact on n-GaN to simplify the process in a flip-chip light-emitting diode (FCLED). The investigated composite metals were Ti∕Al∕Ti∕Au, Cr∕Al∕Cr∕Au, and Cr∕Ti∕Au. The specific contact resistivities of the Ti∕Al∕Ti∕Au, Cr∕Al∕Cr∕Au, and Cr∕Ti∕Au Ohmic contacts on n-GaN were changed from 1.4×10−4, 1.7×10−4, and 1.9×10−4Ωcm2 to 1.3×10−4, 1.1×10−4, and 3.3×10−5Ωcm2, respectively, after 500h of thermal stress. The corresponding operating voltages of FCLEDs with different composite metals were changed by less than 1%. After 96h of thermal stress, the luminous intensities of the three structures decreased by 6.2%, 11.1%, and 1.4%, respectively. The GaN FCLED that was fabricated with Cr∕Ti∕Au as a reflector and an Ohmic contact on n-GaN exhibits good thermal stability and luminous intensity.