Lattice parameters of Sc${}_{\mathsf{x}}$Al${}_{1-\mathsf{x}}$N layers grown on GaN(0001) by plasma-assisted molecular beam epitaxy

Abstract

An accurate knowledge of the lattice parameters of the new nitride Sc${}_{\text{x}}$Al${}_{\text{1-x}}$N is essential for understanding the elastic and piezoelectric properties of this compound as well as for the ability to engineer its strain state in heterostructures. Using high-resolution x-ray diffractometry, we determine the lattice parameters of 100-nm-thick undoped Sc${}_{\text{x}}$Al${}_{\text{1-x}}$N layers grown on GaN(0001) templates by plasma-assisted molecular beam epitaxy. The Sc content $\text{x}$ of the layers is measured independently by both x-ray photoelectron spectroscopy and energy-dispersive x-ray spectroscopy and ranges from 0 to 0.25. The in-plane lattice parameter of the layers linearly increases with increasing $\text{x}$, while their out-of-plane lattice parameter remains constant. Layers with $\text{x}$ $\approx$ 0.09 are found to be lattice matched to GaN, resulting in a smooth surface and a structural perfection equivalent to that of the GaN underlayer. In addition, a two-dimensional electron gas is induced at the Sc${}_{\text{x}}$Al${}_{\text{1-x}}$N/GaN heterointerface, with the highest sheet electron density and mobility observed for lattice-matched conditions.

Cited by in corpus (2)

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• High Mobility Multiple-Channel AlScN/GaN Heterostructures