Green photoluminescence from cubic In0.4Ga0.6N grown by radio frequency plasma-assisted molecular beam epitaxy

We investigate the structural and optical properties of a cubic (In, Ga)N/GaN/(Al, Ga)N heterostructure containing a 185 nm thick ${\mathrm{In}}_{\mathrm{0.4}}{\mathrm{Ga}}_{\mathrm{0.6}}\mathrm{N}$ layer which dominates the optical properties of the sample. The phase purity of the structure is verified by means of transmission electron microscopy while the In content is measured by x-ray diffraction and secondary ion mass spectrometry. The room-temperature band gap of the ${\mathrm{In}}_{\mathrm{0.4}}{\mathrm{Ga}}_{\mathrm{0.6}}\mathrm{N}$ layer is determined by transmission and reflectance measurements to be $\text{2.46±0.03\hspace{0.17em}}\mathrm{eV}.$ This value agrees with the spectral position of the dominating green photoluminescence at 300 K.