From (In,Ga)N top-down nanowires to pseudo-substrates

The band gap of (In,Ga)N spans the entire visible spectral range. Thus, this material is very attractive for applications involving light emission or absorption. The nanowire morphology offers additional benefits such as efficient elastic strain relaxation. At the same time, bottom-up growth faces the challenge that changes in composition typically affect the morphology. Here, it is shown how this challenge can be overcome by combining the growth of thick (In,Ga)N layers by molecular beam epitaxy with the subsequent top-down fabrication of nanowires. Thus, composition and morphology are independently controlled during growth and structuring, respectively. The patterning is based on metal dewetting, which is a scalable approach that can be employed for large wafers. Furthermore, it is explained how such nanowires can serve as the basis for the fabrication of (In,Ga)N pseudo-substrates by coalescence overgrowth. These pseudo-substrates are promising for the epitaxial growth of red light-emitting diodes (LEDs) that require a high In content.