The gate oxide films have been grown at a temperature as low as 450 °C by direct oxidation of silicon. Such a low-temperature oxidation has been realized by employing a precision controlled ion bombardment in an Ar/O2 mixed plasma for the surface activation. Perfectly controlled Ar ions give the bombardment energy for the oxide film growth. Dielectric breakdown fields of 10 MV/cm are achieved. Integration in a total low-temperature device process has been demonstrated by fabricating self-aligned Al-gate metal-oxide-silicon field effect transistor (MOSFET) formed without any heat processing over 450 °C. The precise control of the ion bombardment is quite essential for the low-temperature process.
The effects of the deposition rate and the substrate temperature on the structure and the electrical and optical properties of CdTe film evaporated on an Au-coated glass substrate were investigated, and the film quality is discussed here. It is shown that the crystalline size decreased with the deposition rate and increased with the substrate temperature, and that the stoichiometry of the film was best at the deposition rate of 17 Å sec-1 at room temperature. At a lower deposition rate, the film became Cd-rich and n-type, while it became Te-rich and p-type at a higher deposition rate. The Cd content increased with the substrate temperature. The films deposited at lower rates were polycrystalline and those deposited at higher rates were amorphous. The film deposited at a rate of 17 Å sec-1 –19 Å sec-1 and a substrate temperature of 100°C showed the highest quality of all the films.
H 2 -cleaned sapphire substrate was treated with an electron-beam aiming at polarity-selective growth of GaN film by using metalorganic chemical vapor deposition (MOCVD). It was found that GaN growth on the sapphire substrate treated with an electron-beam was suppressed like GaN growth on a SiO 2 mask. GaN grooves having the fluctuated sidewalls were fabricated as designed by lithography patterns due to the selective growth. The groove sidewalls became smoother after etching by dipping in a KOH aqueous solution. This improvement was enhanced for the grooves oriented along <11 2 0> direction, compared to those along <1 1 00> direction.
High dark conductivity CdTe films have been prepared by a co‐evaporated process of CdTe and Cd. The structural, electrical and optical properties were investigated. Dark conductivity of the film increased monotonically with an increase of the co‐evaporated Cd. The highest dark conductivity of the film obtained in this experiment was 0.54 ohm‐1 cm‐1. The film structure was of the zinc‐blend type with a preferential orientation of the (111) planes parallel to the substrate and fibers. The crystallinity of the dark films was similar to films without Cd doping. This high dark conductivity film will be useful for thin film CdTe solar cells.
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