Hydrogenated amorphous silicon nitride (a-SiNx:H) films have been fabricated by plasma-enhanced chemical vapor deposition at temperatures ranging from 50 to 250 °C. It is found that as soon as the samples are taken out from the reaction chamber and exposed to the atmosphere, the a-SiNx:H films start to oxide. The oxidation processes are monitored using infrared absorption spectroscopy. A model of porous ‘‘fractal-like network’’ structure, which is probably inherent in low-temperature deposition, is proposed to explain why moisture (H2O) in the air can percolate through numerous microvoids into these films. The H2O molecules which percolate into these porous films are active to react with the —Si—N—Si—, —Si—N—H, and —N—Si—-H bonds and to form more chemically stabilized —Si—O—Si—, —Si—O—H, and H—O—H bond configurations with the result of eventual oxidization of the entire nitride films.

Hydrogenated amorphous silicon oxide (a-SiOx:H) films have been fabricated by plasma-enhanced chemical vapor deposition at temperature ranging from 15 to 150 °C. It is found that once these films are taken out from the reaction chamber and immersed into water or exposed to the atmosphere, the Si–H and –Si–Si– bonds in the films start to oxidize. After immersing the films into deionized water, many small gas bubbles are formed upon the films’ surface and these bubbles were collected into sealed tubes and identified as hydrogen gas (H2(g)) using gas chromatography technique. By using infrared absorption spectroscopy and monitoring these oxidation processes at various times, it is clear that at room temperature water (H2O) molecules react with Si–H bonds and –Si–Si– bonds and form more chemically stabilized Si–O–Si, Si–O–H, H–O–H bonds, and H2(g). Study of the Si–H decreasing rates reveals that second-order reaction occurs at the initial stage of oxidation, which is consistent with two adjacent Si–H bonds oxidizing together with one attacking H2O molecule. A model of porous structure, which is probably inherent at low temperature deposition, is proposed to explain why H2O molecules can percolate through the films and eventually fully oxidize these films.

A three-dimensional (3D) fin-shaped field-effect transistor structure based on III-V metal-oxide-semiconductor field-effect transistor (MOSFET) fabrication has been demonstrated using a submicron GaAs fin as the high-mobility channel. The fin-shaped channel has a thickness-to-width ratio (TFin/WFin) equal to 1. The nano-stacked high-k Al2O3 dielectric was adopted as a gate insulator in forming a metal-oxide-semiconductor structure to suppress gate leakage. The 3D III-V MOSFET exhibits outstanding gate controllability and shows a high Ion/Ioff ratio > 105 and a low subthreshold swing of 80 mV/decade. Compared to a conventional Schottky gate metal–semiconductor field-effect transistor or planar III-V MOSFETs, the III-V MOSFET in this work exhibits a significant performance improvement and is promising for future development of high-performance n-channel devices based on III-V materials.

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