Influence of crystal polarity on the properties of Pt/GaN Schottky diodes

Si-doped epitaxial GaN layers with Ga- and N-face polarity were grown by plasma-induced molecular-beam epitaxy (PIMBE) in order to characterize the influence of polarity on the electrical properties of Pt Schottky diodes. Different barrier heights for Pt onto these two materials are obtained from the dependence of the effective barrier height versus ideality factor, determined by I-V measurements to be 1.1 and 0.9 eV for Ga- and N-face GaN, respectively. C-V measurements confirm the greater barrier heights for Ga-face material. A possible explanation for this behavior can be a different band bending of the conduction and valence band, inferred from the self-consistent solution of the Schrödinger-Poisson equation, including polarization-induced surface and interface charges, which result from the different spontaneous polarization in epitaxial layers with different polarity.