Research on epitaxial of 250 nm high quality GaN HEMT based on AlN surface leveling technology

•The interface quality was investigated by testing the surface morphology of the AlN nucleation layer by AlN growth interruption experiments.•A high quality 250 nm thick GaN epitaxial layer was grown. The (0 0 2) plane and the (1 0 2) plane rocking curve had a full width at half maximum of 81 arc seconds and 209 arc seconds.•The electrical properties of the thin-layer GaN HEMT did not decrease, and the room temperature mobility reached 2238 cm2/V·s. GaN HEMT epitaxial materials with different buffer layer thicknesses were grown on 4H-SiC substrates by metal-organic chemical vapor deposition (MOCVD). The interface quality between AlN and GaN was improved based on AlN surface planarization technology. A high quality 250 nm thick GaN epitaxial layer was grown. The (0 0 2) plane and the (1 0 2) plane rocking curve have a full width at half maximum of 81 arc seconds and 209 arc seconds, respectively, and the electron mobility of the heterojunction two-dimensional electron gas reaches 2238 cm2/V·s. The surface topography and electrical properties of the material were measured by atomic force microscopy (AFM) and non-contact Hall tester. It was found that the surface smoothness of the GaN buffer layer and the electron mobility of 2DEG did not change significantly, and the X-rays diffractometer was used to analyze the crystal quality and stress of the GaN epitaxial layer.