Screw-type dislocations due to lattice mismatch in GaP: N/GaP epitaxy

Abstract

Screw-type dislocation arrays were observed in GaP homogeneous epitaxy in which a nitrogen-doped GaP layer was grown on a pulled GaP substrate by the liquid-phase epitaxial method. Observations were carried out by X-ray transmission topography using a Lang camera. The lattice mismatch in this case originated from the doped nitrogen. Screw-type dislocations are favoured as misfit dislocations when a twist occurs about the normal to the interface. It is also shown that the misfit dislocation type depends on the ratio of δ/θ where δ and θ are Δd/d and the twist angle, respectively. From these considerations, it is demonstrated that it is reasonable that screw and 60° dislocations be formed at the interface at δ/θ ≪ 1 and = √3, respectively. Moreover, it is found that the interfacial energy may be expressed as E = E ₀θ’ (A – ln θ') regardless of the type of the misfit dislocation.