Strain cancellation by indium incorporation for the calibration of nitrogen fractions in GaAsN

This paper reports a study of strain cancellation by adding indium to GaAs_1-yN_y epitaxial layers as a method of calibrating the nitrogen fraction y. The aim was to determine the In fraction x in an In_xGa_1-xAs_1-yN_y epitaxial layer which exactly cancels the strain present in a GaAs_1-yN_y layer with the same nitrogen content when grown on a GaAs substrate. This is an alternative to asserting nitrogen fractions in GaAs_1-yN_y layers on the basis of x-ray measurements, when the values and linearity of lattice and elastic constants with nitrogen composition y has not been established. The GaAs_1-yN_y and In_xGa_1-xAs_1-yN_y layers were grown on GaAs (001) substrates using molecular beam epitaxy with an electron cyclotron resonance nitrogen plasma source. Layers have been assessed by high-resolution x-ray diffraction to determine the relationship between the lattice constant of the GaAs_1-yN_y layer and the fraction x of In required to exactly cancel the strain.