Carrier Transport Mechanism at the Interface between Metals and p-Type III–Nitrides Having Different Surface Electronic Structures

We have investigated the carrier transport mechanism for nonalloyed Ni/Au ohmic contacts to p-In 0.15 Ga 0.85 N/GaN superlattices (SLs) and Mg delta (δ)-doped GaN using current–voltage–temperature ( I – V – T ) and specific contact resistance–temperature ( R sc – T ) data. The p-SL and Mg δ-doped GaN contacts show a linear I – V behavior, indicating that the Mg δ doping in the GaN matrix as well as p-SL is very effective in improving the electrical properties of p-ohmic contacts. From the R sc – T and I – V – T measurements, the p-SL and Mg delta-doped GaN contacts show slight temperature-dependence characteristics at the temperatures of ≥293 K. These different behaviors can be described in terms of a reduced energy band-bending, an increased hole carrier density, and a reduced Schottky barrier height.