Features of InN growth by nitrogen-plasma-assisted MBE at different ratios of fluxes of group-III and -V elements

The results of investigations of the effect of the ratios of fluxes of the Group-III and -V elements on the structural and optical properties of an InN film deposited by plasma-assisted molecular-beam epitaxy (MBE) are presented. It is shown that the InN layer consists of free-standing nanocolumns at a flux ratio of III/V $<$ 0.6. InN growth becomes two-dimensional (2D) in the ratio range 0.6 $<$ III/V $<$ 0.9; however, the InN layer has a nanoporous structure. Upon passage to metal-rich conditions of growth (III/V $\sim$1.1), the InN layer becomes continuous. The passage from 3D to 2D growth is accompanied by an increase in the threading-dislocation density. It results in a decrease in the photoluminescence (PL) intensity of InN at room temperature. The electron concentration in the InN layers amounts to $\sim$5 $\cdot$10$^{18}$ cm$^{-3}$, which results in a shift of the PL-signal peak to the wavelength region of 1.73–1.8 $\mu$m and to a shift of the absorption edge to the region of $\sim$1.65 $\mu$m.