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 x 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.

Review of the Recent Progress on GaN-Based Vertical Power Schottky Barrier Diodes (SBDs)

“…Furthermore, the peak electric field at the edges can be reduced by extension of PN junction in depletion layer. However, the p + -GaN implantation method with high-temperature annealing conditions can increase the significant risk and complexity of the p-guard ring fabrication [52][53][54][55][56][57][58].…”