Surface State Spectrum of AlGaN/AlN/GaN Extracted From Static Equilibrium Electrostatics

Abstract

We extract an AlGaN surface state spectrum with a density (DSS) ranging between 1.4 x 10(12) and 4.7 x 10(12) eV(-1)cm(-2). The low DSS is achieved with in situ SiN passivation. DSS is extracted from ungated AlGaN/AlN/GaN heterostructures with varied AlN thicknesses between 0 and 2 nm: increased AlN thicknesses in heterostructures monotonously increase two-dimensional electron gas (2DEG) densities Nsh and AlGaN surface potential energies q phi s, and DSS is extracted with Delta N-sh-Delta phi s correlations. The DSS extraction methodology in this work features calibrated polarization charge values, Hartree approximation-based 2DEG profile calculation, and incorporated C-doped GaN (C-GaN) substrate impact on 2DEG. We also extract the charge neutrality level at the AlGaN surface, which is similar to 0.95 eV below conduction band minimum.