Observation of self-assembled InGaN/GaN superlattice structure grown on N-polar GaN by plasma-assisted molecular beam epitaxy

In this paper, we report on the observation of self-assembled InGaN/(In)GaN superlattice (SL) structure in a nominal “InGaN” film grown on N-polar GaN substrate. 350 nm thick InGaN films were grown at different temperatures ranging from 600 to 690 °C. Structural characterization was conducted via atomic force microscopy, scanning transmission electron microscopy, high-resolution x-ray diffraction, and XRD reciprocal space map. A SL structure was unexpectedly observed on all samples. However, the In content in each layer varied depending on growth temperature. By increasing the substrate temperature to 670 °C, a periodic structure composed of 3 nm In0.26Ga0.74N and 3 nm of GaN with a surface roughness of ∼0.7 nm was achieved. This work establishes a method for the growth of InGaN films with high structural quality on N-polar GaN and opens a new pathway for the design and fabrication of various electronic and optoelectronic devices with enhanced performance.