Fermi Level Movements at the Transition Metal/GaN Interface

Abstract

One of the wide band gap III-V compound semiconductor, GaN, is expected to be utilized for the high-functional optical device due to its superior chemical-stability. In the present study, it has been investigated what is the most important factor determining the position of the Fermi level at the interface between GaN and depositing metal through studying interfacial electrical properties, bonding state and thermal stability. Under ultrahigh vacuum, Ni, Pd, Pt, Au, Ti, Cr and Al were in-situ deposited on both types of GaN grown by MOCVD and studied by photoemission, AES depth profiles and AFM. Through the band bending analysis, it can be recognized that unless the new layers, like either TiN or CrGaN, are not formed, the band bending depends more upon the solid state electronegativity than the work function of the contacting metal. Most of metals were uniformly deposited, and especially Ti, Cr, and Al were reacting with GaN at the depositing instant resulting in the novel phase mixing with N and Ga segregation. On the other hand Ni, Pd, and Pt did not form any nitride and their on-set temperature for reacting with GaN were different (TNi<TPd<TPt).