Atomic-column resolution quantitative composition analysis of AlN interlayer in MOCVD-grown AlGaN/AlN/GaN heterostructure using HAADF-STEM

Abstract

Quantitative compositional analysis using high-angle annular dark-field scanning transmission electron microscopy was performed for a metal-organic chemical vapor deposition-grown AlGaN/AlN/GaN heterostructure at atomic-column resolution. In addition, the effects that different concentrations of Al in the AlN interlayer had on the electronic properties were evaluated. The maximum Al concentration in the AlN interlayer was 0.41, and the compositional grading at the upper and lower AlN interfaces resulted in an asymmetric broadening of the interface. Calculations show that increasing the Al concentration in the AlN interlayer leads to an approximately linear increase in the two-dimensional electron gas sheet density. The alloy scattering is also effectively suppressed when the Al concentration is greater than 0.4.