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

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.

Automated summary

The density of AlGaN surface states was extracted and analyzed, showing the influence of AlN thickness on 2DEG density and AlGaN surface potential. The accuracy and factors affecting the DSS extraction method were demonstrated.