Polarization-Driven-Orientation Selective Growth of Single-Crystalline III-Nitride Semiconductors on Arbitrary Substrates

III-nitride semiconductor films are usually achieved by epitaxial growth on single-crystalline substrates (sapphire, silicon (Si), and silicon carbide). It is important to grow these films on non-epitaxial substrates of interest such as polycrystalline substrates for exploring novel applications in electronics and optoelectronics. However, single-crystalline III-nitride films with uniform orientation on non-epitaxial substrates have not yet been realized, due to the lack of crystallographic orientation of the substrates. Here, this work proposes a strategy of polarization-driven-orientation selective growth (OSG) and demonstrate that single-crystalline gallium nitride (GaN) can in principle be achieved on any substrates. Taking polycrystalline diamond and amorphous-silicon dioxide/Si substrates as typical examples, the OSG is demonstrated by utilizing a composed buffer layer consisting of graphene and polycrystalline physical vapor deposited (PVD) aluminium nitride (AlN). The polarization of the PVD AlN can effectively tune the strength of interfacial orbital coupling between AlN nuclei and graphene at different rotation angles, as confirmed by atom-scale first-principles calculations, and align the AlN nuclei to form a uniform orientation. This consequently leads to continuous single-crystalline GaN films. The ability to grow single-crystalline III-nitrides onto any desired substrates would create unprecedented opportunities for developing novel electronic and optoelectronic devices.