High-Performance N-Polar GaN/AlGaN Metal-Insulator-Semiconductor High-Electron-Mobility Transistors with Low Surface Roughness Enabled by Chemical-Mechanical-Polishing-Incorporated Layer Transfer Technology

This article presents the utilization of the chemical-mechanical polishing (CMP) method to fabricate high-performance N-polar GaN/AlGaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) through layer transfer technology. The nucleation and buffer layers were removed via CMP to attain a pristine N-polar GaN surface with elevated smoothness, featuring a low root-mean-square (RMS) roughness of 0.216 nm. Oxygen, carbon, and chlorine impurity elements content were low after the CMP process, as detected via X-ray photoelectron spectroscopy (XPS). The electrical properties of N-polar HEMTs fabricated via CMP exhibited a sheet resistance (Rsh) of 244.7 omega/sq, a mobility of 1230 cm2/V center dot s, and an ns of 2.24 x 1013 cm-2. Compared with a counter device fabricated via inductively coupled plasma (ICP) dry etching, the CMP devices showed an improved output current of 756.1 mA/mm, reduced on-resistance of 6.51 omega center dot mm, and a significantly reduced subthreshold slope mainly attributed to the improved surface conditions. Meanwhile, owing to the MIS configuration, the reverse gate leakage current could be reduced to as low as 15 mu A/mm. These results highlight the feasibility of the CMP-involved epitaxial layer transfer (ELT) technique to deliver superior N-polar GaN MIS-HEMTs for power electronic applications.