Al‐Rich AlGaN Channel/AlN Buffer High‐Electron‐Mobility Transistor with Superlattice Structure

In this study, the development of AlGaN‐based high‐electron‐mobility transistors (HEMTs) grown via metal‐organic chemical vapor deposition on 4H‐SiC substrates is presented, by introducing an optimized superlattice (SL) structure between the AlN buffer and AlGaN channel layers. The insertion of a 300 nm SL structure achieves a 17.3% relaxation in the compressive stress inherent in the AlGaN channel layer, as confirmed by reciprocal space mapping analysis using X‐ray diffraction. Atomic force microscopy measurements reveal a reduction in surface roughness from 1.7 to 1.2 nm, demonstrating improved surface topography. Photoluminescence analysis indicates a composition pulling effect caused by stress variations, leading to differences in Al composition in the AlGaN channel, which validates the stress relaxation mechanism induced by the SL structure. Direct current characterization shows a peak drain saturation current of 7.9 mA mm −1 , representing a 155% improvement over the baseline structure without a SL. These findings suggest the potential of the SL structure as a scalable strain management strategy to improve epitaxial and device characteristics for high‐performance AlGaN channel HEMTs.