Investigation of Electrical and Interfacial Properties of Improved Ohmic Contact on p-Type GaN

Abstract

Ohmic contacts on p-GaN with Pd/Pt/Au metallization scheme deposited at room temperature and elevated temperature were prepared to study the effect of metal deposition temperature on the contact properties. The specific contact resistance decreased by the heat-treatment of the p-GaN sample in an ultra-high vacuum environment. The in-diffusion of Au atoms and out-diffusion of Pd atoms are further suppressed by the diffusion barrier layer deposited at elevated temperature. The interfacial microstructure shows that the formation of Pd gallides is enhanced. The improvement of the electrical properties is attributed to the reduction of effective Schottky barrier height at the Pd/p-GaN interface by the XPS analyze and calculation, due to the desorption of the surface carbon or oxide contaminations of p-GaN.

The Significant Effect of Carbon and Oxygen Contaminants at Pd/p‐GaN Interface on Its Ohmic Contact Characteristics

“…However, once undergoing a high‐temperature annealing process, Au atoms could inevitably diffuse into the contact metal layer through some defects and grain boundaries populating the metal stacks. In our earlier results, [ 26 ] we found that a diffusion barrier deposited at an elevated temperature more effectively suppresses the indiffusion of Au atoms and outdiffusion of Pd atoms, which promotes the Ohmic contact characteristics. In addition to deposition temperature, we also noted that carbon and oxygen contaminants have a significant effect on Au indiffusion behaviors and contact resistance.…”