Features of formation of In$_x$Ga$_{1-x}$N bulk layers in the immiscibility gap of solid solutions ($x$ $\sim$ 0.6) by molecular beam epitaxy with plasma nitrogen activation

In this paper, the features of the formation of bulk InGaN layers with an indium content of $\sim$ 60% in the immiscibility gap of InGaN ternary solid solutions by the method of molecular-beam epitaxy with plasma nitrogen activation are studied. The structures under study were grown on sapphire substrates, while the epitaxy temperature and the ratio of metal (In + Ga) and activated (atomic) nitrogen fluxes were varied. It has been demonstrated that the rates of thermal decomposition and phase separation for In$_{0.6}$Ga$_{0.4}$N ternary solutions depend nonmonotonically on the growth temperature in the range $T_{\mathrm{gr}}$ = 430–470$^\circ$C. It is shown that InGaN thermal decomposition processes occur on the growth surface and lead to the appearance of surface phases of metallic In and binary InN, while phase separation leads to the appearance of InGaN phases of various compositions throughout the volume of the deposited InGaN layer. It is shown that, in the temperature range under study, phase separation is determined by surface diffusion, which can be suppressed by growth under highly nitrogen-enriched conditions, which made it possible to obtain homogeneous InGaN layers with an In content of In $\sim$ 60% during high-temperature ($T_{\mathrm{gr}}$ = 470$^\circ$C) growth. It is shown that the suppression of InGaN thermal decomposition processes is decisive in achieving effective interband luminescence of the obtained structures, while the presence of phase separation affects the radiative properties of InGaN layers to a lesser extent, at least in the region of low ($T$ = 77 K) temperatures.