PA MBE growth of intermediate-composition InGaN layers for red and near-IR laser sources

This paper presents the results of studying the growth of InGaN layers with a high (50–80%) indium content by molecular beam epitaxy with nitrogen plasma activation on sapphire substrates with GaN/AlN buffer layers. It is shown that the processes of dissociation and phase separation of the growing InGaN layer, which occur in structures with an indium fraction of about 50%, cannot be suppressed due to the transition to a lower temperature growth (470$^\circ$C $\to$ 390$^\circ$C) without significant degradation of the crystalline quality of the formed structures and a sharp decrease in their emissivity. As an alternative approach to suppressing diffusion processes on the growth surface and, as a result, obtaining homogeneous InGaN layers with an [In] content $\sim$50%, high-temperature (470$^\circ$C) growth under highly nitrogen-enriched conditions (flux ratio III/V $\sim$0.6) was tested. The InGaN layers grown in this way show intense photoluminescence, while at the same time showing no signs of phase separation according to X-ray diffraction data. This is critically important for the possibility of implementing optical amplification and laser generation in such structures in the red region of the spectrum and in the immediately adjacent part of the near infrared region.