Evolution and analysis of nitride surface and interfaces by statistical techniques: A correlation with RHEED through kinetic roughening

Abstract

In-situ RHEED and ex-situ AFM characterizations have been employed to investigate transformations of surface topography with the thickness of PAMBE grown AlGaN and InGaN on GaN. The ternary alloys have been grown with identical growth-front roughness as confirmed by XRR and RHEED observations. The spottier RHEED has been observed with increased thickness of the InGaN as opposed to streakier behavior of AlGaN. We have noticed incremental nature of RMS roughness, skewness and kurtosis of InGaN surface compared to GaN or AlGaN from AFM as evident by final spotty RHEED for InGaN. However, the analyzed fractal dimension is lower for InGaN as opposed to AlGaN (D AlGaN f >D GaN f >D InGaN f ). From the kinetic roughening perspective of adatoms, the experimental evidences lead to the high correlation between binding energy of the cluster atoms (E AlN b >E GaN b >E InN b ) and the modified DDA growth model with dissociation and evaporation to confirm the efficacy of the study. The initial streaky and spotty RHEED of InGaN and AlGaN, respectively, can be attributed to their E b that causes smoothing and roughening of the GaN surface due to adatoms surface mobility behavior. Therefore, the fractal description reveals the fact during formation of nitride hetero-interface while other AFM results describe the top surface.