We report on structural and electrical properties of tantalum penta oxide (Ta2O5) material with a high dielectric constant grown from a penta ethoxy tantalum [Ta(OC2H5)5] liquid source by the plasma-enhanced liquid source chemical vapor deposition (PE-LS-CVD) technique. We have investigated several basic plasma deposition conditions. Structural properties investigated by θ-2θ X-ray measurements showed the amorphous nature of the films, and Auger electron spectrosopy (AES) and secondary ion mass spectroscopy (SIMS) indicated growth of Ta2O5 films having proper stoichiometry (Ta/O=0.4). Optical transmission spectroscopy showed that the band gap (E g) of Ta2O5 is 5.28 eV. Electrical measurements performed on Au/Ta2O5/n, p-Si metal oxide semiconductor (MOS) structure exhibited very well defined capacitance-voltage (C-V) characteristics with flat band voltage as low as -0.1 eV, low leakage current, high breakdown voltage and high dielectric constant (25-38). As a hitherto unreported step in Ta2O5 processing we also performed rapid thermal (RTA) annealing at 700°C and 900°C for 5 min which resulted in much improved electrical properties. All results suggest growth of high-quality Ta2O5 films from a carbon-based Ta liquid source, due to an effect of plasma-enhanced deposition process.

Infrared absorption spectroscopy has been performed on hydrogenated and deuterated n-type silicon-doped GaAs. It reveals the presence of a sharp vibrational mode at 890 cm−1 in hydrogenated samples and at 637 cm−1 in deuterated ones. These bands are absent in undoped GaAs. Analysis of the isotopic shift frequency reveals that the band is associated with a hydrogen–arsenic bond where arsenic is supposed to sit as a first nearest neighbor of the silicon donor atom giving rise to (SiAs3)As-H complexes. Isochronal annealing experiments show the direct correlation between the absorption line intensity and the amount of neutralized donors, confirming the view that the extra electrons of the silicon donors are involved in the hydrogen–arsenic bonds.

No abstract

We report the effect of annealing and sulfur (S) passivation of GaAs surface on the interface characteristics and interdiffusion problem in ZnSe/GaAs heterostructures whose ZnSe layers are grown by atomic layer epitaxy (ALE) and metalorganic molecular beam epitaxy (MOMBE). The photoluminescence (PL) intensity of self-activated centers created due to interdiffusion at 500°C in the conventionally grown sample is 3-14 times higher than that in the S-passivated sample. Secondary ion mass spectroscopy (SIMS) data suggest that after annealing, Ga and As concentration in the ZnSe epilayer is lower in S-passivated materials. These features suggest that heterostructures are thermally stable in S-passivated material. As a result of S-passivation, full width at half maximum (FWHM) values of X-ray rocking curves are greatly reduced and we could, without postgrowth annealing, achieve well-defined C-V characteristics of a metal/pseudoinsulating ZnSe/GaAs metal-insulator-semiconductor (MIS) diode. Sulfur passivation is an important tool for the fabrication of high-quality heterostructures of II-VI and III-V semiconductors.