X-ray determination of the composition of partially strained group-III nitride layers using the Extended Bond Method

An extension of Bondʹs method for determining precision lattice parameters serves to determine the lattice parameters of (strained) unit cells of a film from the peak positions of the film alone. We call this measurement and evaluation procedure the ‘Extended Bond Method’ (EBM). The procedure avoids recurrence to possibly unreliable or unavailable lattice parameters of the substrate; it is successful, irrespective of whether a layer is pseudomorphically strained, partially relaxed, or completely relaxed, as long as the strain can be described as a uniaxial distortion parallel to the growth direction. Using a mathematical/graphical evaluation procedure, the chemical composition of a layer is obtained, once its strained lattice parameters have been determined. The technique is of particular value for the determination of the strain and the composition of group-III nitride layers.