Hardening Effect of GaP_1-<i>x</i>N_<i>x</i>and GaAs_1-<i>x</i>N_<i>x</i>Alloys by Adding Nitrogen Atoms

Abstract

We investigated the strain relaxation process of GaP 1- x N x /GaP and GaAs 1- x N x /GaAs in order to clarify their mechanical characteristics by adding nitrogen atoms. It was observed by transmission electron microscopy (TEM) that the critical thicknesses were greater and the generation rates of the misfit dislocations were slower in the GaP 1- x N x and GaAs 1- x N x layers than those in the GaP layer with a similar lattice mismatch. The critical thickness of the GaAs 1- x N x layer was greater than that of the GaP 1- x N x layer for the same nitrogen composition of 2%. The direction of higher crack density was orthogonal to that of the higher misfit dislocation density. These results indicate that the propagation of dislocations is prevented in III–V–N alloys such as GaP 1- x N x and GaAs 1- x N x , so that these alloys are harder than III–V compounds that lack nitrogen atoms. This feature could be attributed to the dislocation pinning and alloy hardening effects due to nitrogen atoms.