Revealing inhomogeneous Si incorporation in GaN on nanometer scale by electrochemical etching
Typical methods of doping quantification are based on spectroscopy or conductivity measurements. The spatial dopant distribution assessment with nanometer-scale precision is limited usually to one or two dimensions. Here we demonstrate an approach to detect three-dimensional dopant homogeneity in GaN:Si layers using electrochemical etching (ECE). We impose non-uniform embedment of Si atoms during crystal growth plasma-assisted molecular beam epitaxy by intentional modification of the growth front morphology. In this work we show that local Si concentration differences of about three times are distinguished using ECE with spatial resolution of about 50 nm. This places ECE as a simple and quantitative probing tool for local three-dimensional conductivity homogeneity assessment and could be important both for fundamental studies of crystal growth physics and impurity incorporation as well as for ion-implanted structures and post-processing device control.