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Recess structure is one of the main schemes for insulated-gate E-mode GaN transistors. In this work, selective area growth (SAG) is proposed to fabricate damage-free recess-gate device, and related progresses regarding process optimization and structure evolution have been reviewed. Firstly, the SAG process has been optimized by interface separation (conduction interface and regrowth interface) and n-type Si impurity removal to achieve high-quality AlGaN/GaN heterostructure. Compared to the traditional etching method, the feasibility and superiority of SAG scheme are demonstrated for realizing E-mode Al2O3/GaN MISFET with small Vth hysteresis. Then, by inserting an in situ AlN interlayer, the SAG Al2O3/AlN/GaN MISFET yields improved frequency dispersion and gate channel conduction performances. To further enhance the channel conduction, the SAG partially recess-gate Al2O3/AlGaN/GaN MIS-HFET structure is proposed, by which both high Vth and high-field-effect channel mobility have been achieved. Those results indicate that SAG method gives a perspective way for insulated-recess-gate GaN transistors fabrication. [ABSTRACT FROM AUTHOR]

In this work, H2O-Al2O3/O3-Al2O3 insulating bilayers were grown on GaN by atomic-layer deposition (ALD) technique using H2O vapor and O3 as oxidants. The electrical and material properties show that the H2O-Al2O3/O3-Al2O3 stack structure appeared to be an appropriate dielectric for GaN MOS devices that had low leakage current densities, high breakdown voltages, and good capacitance-voltage ( C-V) curves. The H2O-Al2O3 interlayer between the O3-Al2O3 and GaN efficiently prevented the GaN surface from oxidizing by ozone oxidant by its strong oxidizing power. By taking photo-assisted C-V measurements, it was found that the deep interface state densities at the Al2O3/GaN interface reduced, while increasing the thicknesses of the H2O-Al2O3 interlayer restricted the 'Vth shift' phenomenon and improved the stability and reliability of the GaN MOS devices. [ABSTRACT FROM AUTHOR]

A nonvolatile memory (NVM) based on an amorphous-indium–gallium–zinc oxide (a-IGZO) thin-film transistor (TFT) with defect-engineered gate insulator was demonstrated. The gate insulator was a blocking alumina/storage alumina/tunneling alumina stack structure, which was simply assembled in a single atomic layer deposition step. The memory device showed a positive shift of threshold voltage as large as 14.4 V after +20 V, 1 s programming. In contrast, the memory erasing was not sensitive to negative gate voltage in the dark. Once programmed, the memory can only be light erased. Furthermore, the light combined with a negative bias improved the erasing speed effectively. In addition, a 10-year memory window as large as 7.5 V was extrapolated at room temperature with a charge loss of 34.7%. Based on the observation of blisters in the storage alumina layer after high temperature annealing, Fourier transform infrared spectroscopy measurement and first-principles calculations, the high electron storage capacity can be attributed to the deep defect levels in the storage alumina layer, which were originated from hydrogen impurity. This a-IGZO TFT charge trapping NVM with high performance and simple process is a candidate device for the application of fully functional transparent system on panel. [ABSTRACT FROM AUTHOR]

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.