Search

The InAlN alloy system has bandgap energies that span the entire visible range and is a promising candidate for bandgap engineering. To facilitate bandgap engineering, the bandgap bowing for the entire composition range must be well characterized. In rich InxAl1−xN (x > 0.60), films were grown via plasma assisted molecular beam epitaxy on freestanding GaN substrates. The InxAl1−xN film compositions were determined using high resolution X-ray diffraction. On-axis 0002 ω-2θ scans were used to determine the c spacing of the films, reciprocal space maps of the 1 ¯ 015 peaks were used to determine that the films were completely relaxed, and the film compositions were calculated from that information assuming Vegard's law. The bandgaps were independently measured using absorbance spectroscopy and fitting to the linear region of a Tauc plot (dependence of α2 hν on hν) as determined by interpolating the second derivative of the data and selecting a region of low curvature. Compared with the literature, the data were fit to a composition-independent bandgap bowing model, and a bowing parameter of b = 4.0 ± 0.2 eV was calculated, which is consistent with previous results. [ABSTRACT FROM AUTHOR]

Boron is a difficult material to use in a molecular beam epitaxy (MBE) reactor due to its high melting point as a pure compound. Consequently, there is interest in exploring alternative sources for B in MBE. In this paper, the authors detail the construction and operation of a novel BBr3 injection system for plasma-assisted MBE growth and show results for BGaN thin films grown using readily available low purity BBr3 as a proof of concept for the source. The BBr3 system enables the growth of coherent BGaN films with a concentration up to 3% B on the group III site and thicknesses up to 280 nm as determined by high resolution x-ray diffraction. Atom probe tomography and secondary ion mass spectroscopy results of a B0.03Ga0.97N film indicate a high level of Br impurity on the order of 1 × 1019 atoms/cm3 and atmospheric contamination consistent with a low purity source. BBr3 is successful as a B source for high crystal quality BGaN films; however, the Br incorporation from the source limits the applications for this material. [ABSTRACT FROM AUTHOR]

Incorporating boron into gallium nitride to make BxGa1-xN solid solutions would create an avenue for extreme alloys due to the fact that wurtzite phase BN has a larger band gap and smaller lattice parameters compared to GaN. In this paper, the authors report the growth of high crystal quality, random alloy BxGa1-xN thin films with x up to 3.04% grown on (0001) Ga-face GaN on sapphire substrates using plasma assisted molecular beam epitaxy and BBr3 gas as a B source. High resolution x-ray diffraction was used to measure both the c plane spacing and the strain state of the films. It was determined that the films were fully coherent to the GaN substrate. Elastic stress-strain relations and Vegard's law were used to calculate the composition. Atom probe tomography was used to confirm that the BxGa1-xN films were random alloys. In addition to demonstrating a growth technique for high crystal quality BxGa1-xN thin films, this paper demonstrated the use of BBr3 as a novel B source in plasma assisted molecular beam epitaxy. [ABSTRACT FROM AUTHOR]