Position of fermi level on Al0.2Ga0.8N surface and distribution of electric field in Al0.2Ga0.8N/GaN heterostructures without and with AlN layer

Abstract

Position of Fermi level on Al0.2Ga0.8N surface and distribution of electric field in Al0.2Ga0.8N/GaN transistor heterostructures without and with AlN layer were studied experimentally using contactless electroreflectance and theoretically solving Schrodinger-Poisson equation with various surface boundary conditions. It has been observed that the thin AlN layer changes very strongly the distribution of electric field in this heterostructure but the Fermi level position on Al0.2Ga0.8N surface does not change significantly. Its position is the same within experimental uncertainly (i.e., ∼0.5 eV below conduction band) for both bulk Al0.2Ga0.8N and Al0.2Ga0.8N/GaN heterostructures.