In this letter, partial recessed-gate AlAl ₂ O ₃ /AlGaN/GaN MISFET is experimentally demonstrated based on selective-area growth. The device features different contents of Al in the AlGaN barriers that were grown in the recessed and accessed regions that contributed to a higher $\text{V}_{\textsf {th}}$ and lower ON-resistance. As a result, it achieves a positive shift in ${V}_{\textsf {th}}$ as compared to the reference (from 1.8 to 2.5 V). Besides, this method accomplished the highest reported peak $\mu _{\textsf {FE}}$ value of 2033 cm ² / $\textsf {V}\cdot \textsf {s}$ and a lower gate channel sheet resistance of $519~\Omega /\Box $ (access region, ${R}_{\textsf {sh}} $ of $418~\Omega /\Box $ ) owing to reserving damage-free AlGaN/GaN hetero-structure in the recessed-gate. Notably, the formed device also exhibits a low hysteresis, low gate leakage, and a slight current collapse.

In this work, we have comprehensively investigated the degradation behaviors and mechanism of 1.2 kV silicon carbide (SiC) metal oxide semiconductor field-effect transistors (MOSFETs) under repetitive surge current stress. The experimental results show that the negative drift of threshold voltage ( $\textit{V}_{\text{th}}$ ) is related to the gate turn-off voltage and the surge current. The gate leakage current ( $\textit{I}_{\text{gss}}$ ) increases by about one order of magnitude after the stress. The deterioration of the electrical parameters is considered to be the gate oxide degradation associated with the increase of SiC/SiO $_{\text{2}}$ interface traps. By using the low-frequency noise (LFN) technique, it is demonstrated that the trap density of the device with the most severe degradation after the stress becomes 3.5 times the initial one. On the other hand, we observed that the voltage drop ( $\textit{V}_{\text{sd}}$ ) of the body diode and on-resistance ( $\textit{R}_{\text{ds(\biosc{on})}}$ ) increased. It is attributed to the cumulative degradation process of package with the appearance of fatigue in the bond wire induced by the thermo-mechanical stress during the surge test. This work can serve as a valuable reference for the reliability of SiC MOSFETs.

In this paper, a normally off Al ₂ O ₃ /AlN/GaN MISFET on Si substrate for achieving high threshold voltage stability and uniformity is obtained based on selective area growth. A thin AlN space layer (SL, ~1 nm) is adopted to GaN-based template, and the AlGaN/GaN heterostructure is selectively grown on the template to naturally form a recessed structure. By insertion of the AlN SL, the Al ₂ O ₃ /AlN/GaN interface trapping and scattering effects are effectively suppressed. As a result, a low threshold voltage hysteresis (Δ V _th , 80 mV at maximum gate sweep voltage of 10 V by dc I-V measurement and smaller than 200 mV in linear region by pulse I-V measurement) and a high peak field-effect mobility (μ _FE ) of 192 cm ² /V·s are obtained in Al ₂ O ₃ /AlN/GaN MISFET. It is a significant improvement compared with Al ₂ O ₃ /GaN MISFET without AlN SL. The Al ₂ O ₃ /AlN/GaN MISFET also exhibits a maximum drain current (I _d,max ) of 620 mA/mm, a low on-resistance (R _ds , _ON ) of 9.6 Ω·mm, and a high uniformity of V _th (2.5 ± 0.1 V).

The Schotty-type p-GaN gate high-electron-mobility transistors (HEMT) feature a unique gate structure. A comprehensive understanding of the charge control mechanism in the p-GaN gate region is a fundamental step for the optimization of this technology. In this work, a physics-based analytical model is presented which takes into consideration all the capacitive effects from gate metal deep into the GaN buffer. According to our analysis, the p-GaN layer can be either partially depleted by the metal/p-GaN Schottky junction or fully depleted, depending on the doping concentration and thickness of the p-GaN layer. Our model accurately captures the charge control properties under both conditions and is validated against TCAD numerical simulations. For a certain p-GaN thickness, a lightly doped p-GaN leads to a full-depletion condition, such that the acceptor concentration directly affects the band diagram at AlGaN/GaN interface. The ${V}_{\text {th}}$ of the HEMT increases quickly with acceptor concentration in p-GaN. With sufficiently high acceptor concentration in p-GaN, the device reaches the partial-depletion condition, the acceptor concentration loses its influence over the band diagram at the location of the AlGaN/GaN interface, since the Fermi-level at the AlGaN surface is pinned near the valence band of p-GaN. The ${V}_{\text {th}}$ starts to decrease with acceptor concentration, but at a relatively slow rate. The maximum ${V}_{\text {th}}$ is obtained near the boundary between partial-and full-depletion conditions. In consideration of the process margin, the device designed with a partially depleted p-GaN is preferable, since it ameliorated the ${V}_{\text {th}}$ sensibility against acceptor concentration.

Graphitic carbon nitride (g−CN), a promising visible-light-responsive semiconductor material, is regarded as a fascinating photocatalyst and heterogeneous catalyst for various reactions due to its non-toxicity, high thermal durability and chemical durability, and “earth-abundant” nature. However, practical applications of g−CN in photoelectrochemical (PEC) and photoelectronic devices are still in the early stages of development due to the difficulties in fabricating high-quality g−CN layers on substrates, wide band gaps, high charge-recombination rates, and low electronic conductivity. Various fabrication and modification strategies of g−CN-based films have been reported. This review summarizes the latest progress related to the growth and modification of high-quality g−CN-based films. Furthermore, (1) the classification of synthetic pathways for the preparation of g−CN films, (2) functionalization of g−CN films at an atomic level (elemental doping) and molecular level (copolymerization), (3) modification of g−CN films with a co-catalyst, and (4) composite films fabricating, will be discussed in detail. Last but not least, this review will conclude with a summary and some invigorating viewpoints on the key challenges and future developments.