The InN percent in metalorganic chemical vapor deposition (MOCVD) and atomic layer epitaxy (ALE) grown InGaN was found to be significantly influenced by the amount of hydrogen flowing into the reactor. The temperature ranges for this study are 710–780 °C for MOCVD, and 650–700 °C for ALE. For a given set of growth conditions, an increase of up to 25% InN in InGaN, as determined by x-ray diffraction, can be achieved by reducing the hydrogen flow from 100 to 0 sccm. Additionally, the hydrogen produced from the decomposition of ammonia does not seem to change the InN percent in the films, indicating that the ammonia decomposition rate is less than 0.1%. The phenomenon of having hydrogen control the indium incorporation was not reported in the growth of any other III–V compound previously studied.
Electrical characterization of AlN/GaN interfaces was carried out by the capacitance-voltage (C-V) technique in materials grown by metalorganic chemical vapor deposition. The high-frequency C-V characteristics showed clear deep-depletion behavior at room temperature, and the doping density derived from the slope of 1/C 2 plots under the deep depletion condition agreed well with the growth design parameters. A low value of interface state density D it of 1 ϫ10 11 cm Ϫ2 eV Ϫ1 or less around the energy position of E c Ϫ0.8 eV was demonstrated, in agreement with an average D it value estimated from photoassisted C-V characteristics.
A method for enhancing effective Schottky barrier heights in III-V nitride heterostructures based on the piezoelectric effect is proposed, demonstrated, and analyzed. Two-layer GaN/Al x Ga 1Ϫx N barriers within heterostructure field-effect transistor epitaxial layer structures are shown to possess significantly larger effective barrier heights than those for Al x Ga 1Ϫx N, and the influence of composition, doping, and layer thicknesses is assessed. A GaN/Al 0.25 Ga 0.75 N barrier structure optimized for heterojunction field-effect transistors is shown to yield a barrier height enhancement of 0.37 V over that for Al 0.25 Ga 0.75 N. Corresponding reductions in forward-bias current and reverse-bias leakage are observed in current-voltage measurements performed on Schottky diodes.
We report on the deposition of AlyInxGa1−x−yN in the (0<y<0.15) and (0<x<0.14) composition range by metalorganic chemical vapor deposition. AlInGaN quaternary alloys offer a lattice-matched platform for InGaN-based light emitting heterostructure devices. Epitaxial growth of AlInGaN on (0001) sapphire substrates has been achieved at 750 °C. Alloy composition, lattice constants, and band gaps were obtained by energy dispersive spectroscopy, x-ray diffraction, and room temperature PL. Band edge emissions dominate the PL spectra of these quaternary films. Preliminary data suggest that the lattice constant of AlInGaN can be deduced from chemical composition using Vegard’s law, indicating solid solution in the grown quaternary films.
The electrical characteristics of Ni and Ti Schottky barriers on n-Al0.15Ga0.85N on SiC were investigated. We report that the barrier height for Ni on n-Al0.15Ga0.85N was about 1.26 eV and about 1 eV or less for Ti. These barrier heights are about 0.3–0.4 eV larger than those for Ni and Ti on n-GaN, which are in good agreement with Schottky model predictions.
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