Highly Reflective Nonalloyed Ni/Ag/Pt Contact to Mg–Si Codoped p-GaN for Enhanced Efficiency of Light-Emitting Diodes

Abstract

The authors report enhanced efficiency of GaN-based light-emitting diodes (LEDs) fabricated with highly reflective nonalloyed Ni/Ag/Pt contact. The Ni/Ag/Pt contact formed on the Mg–Si codoped p-GaN produced the low specific contact resistance of 7.9×10−4 Ωcm2 under as-deposited condition, which is comparable to the reference reflector (annealed at 500 °C for 1 min in oxygen ambient). Current–voltage-temperature measurements and the secondary ion mass spectroscopy revealed that the ohmic mechanism of the nonalloyed Ni/Ag/Pt contact is due to the more generated deep-level states associated with Mg–Si codoping, which act as the efficient hopping centers for the carrier transport at the contact/p-GaN interface. Due to the absence of interfacial reaction, the nonalloyed Ni/Ag/Pt contact showed much higher optical reflectivity (93.4% at 450 nm) as compared to the annealed sample (57.7%), resulting in a 40.5% brighter light output power as compared to the reference LEDs.