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 (R_sh) of 244.7 Ω/sq, a mobility of 1230 cm²/V·s, and an n_s of 2.24 × 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 Ω·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 μA/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.

A high-performance temperature sensor based on a p-GaN/AlGaN/GaN hybrid anode diode (HPT-HAD) fabricated by hydrogen plasma treatment is demonstrated. The sensor exhibits accurate and stable temperature responses from 73 to 573 K. The forward anode voltage is linearly proportional to the temperature over the measured temperature range at a fixed current. At a forward current density of 10⁻⁷ mA/mm, the device achieves a maximum sensitivity of 1.93 mV/K. The long-time anode current stress measurement reveals that the HPT-HAD shows almost no degradation even at 573 K for 1 h at a current of 100 μA, and the anode voltage shifts only 120 mV at 573 K for 1000 s at 1 nA. This work shows that the HPT-HAD temperature sensor can be reliably operated over a wide temperature range from cryogenic to high temperatures, so can be used in a variety of extreme environments.

The effect of tetramethylammonium hydroxide (TMAH) treatment prior to gate dielectric deposition on the performance of recessed-gate AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) was investigated. Through the use of TMAH wet etching, a low roughness etched surface of 0.173 nm was obtained. The capacitance–voltage characteristics of MIS heterostructures showed that the interface states reduced by one order of magnitude. When the temperature was increased to 473 K, the treated MIS-HEMTs delivered a small threshold voltage shift (ΔV _TH) of ∼−0.53 V. From the dynamic measurement, the ΔV _TH obtained without treatment was observed more severely (∼−1 V) when compared to the treated one (∼−0.01 V).

This work presents a comparative study of GaN metal-insulator-semiconductor high-electron-mobility-transistors (MIS-HEMTs) employing LPCVD-SiNx/ALD-AlN or PEALD-SiO2/ALD-AlN dielectric stacks. The SiNx/AlN MIS-HEMTs exhibit a minimal threshold voltage shift ( $\Delta {V}_{\text {TH}}$ ) of −0.24 V with an on/off current ratio up to $10^{{8}}$ under $150~^{\circ }$ C, compared to $\Delta {V}_{\text {TH}}=2.0$ V for SiO2/AlN MIS-HEMTs. Under gate bias stress, SiNx/AlN devices show $\Delta {V}_{\text {TH}}$ of −0.90 V (positive) and −0.45 V (negative), versus −1.75 and 3.31 V for SiO2/AlN devices. After maintaining $10^{{4}}$ s of off-state drain-bias stress, SiNx/AlN MIS-HEMT achieves a small $\Delta {V}_{\text {TH}}$ of −0.45 V. The improved stability is attributed to the better interface quality of SiNx/AlN stack, enabled by the low-pressure chemical vapor deposition (LPCVD) process and nitrogen-rich environment. These findings underscore the potential of LPCVD-SiNx/ALD-AlN dielectric stacks in advancing GaN MIS-HEMTs for high-performance and reliable power switching applications.