Toward ferroelectric AlN/GaN heterostructures and sputtered III-N thin films with metal organic chemical vapor deposition-like texture

Merging III-N-technology and wurtzite ferroelectricity could enable novel devices with enhanced functionality, for instance, harsh environment ferroelectric non-volatile memories and neuromorphic components. However, no scalable fabrication approach to achieve this fusion is available to date, as wurtzite ferroelectrics such as Al1-xScxN are hard to synthesize by metal organic chemical vapor deposition (MOCVD), the standard growth method for commercial III-N-devices. Sputtering as another high-throughput method does so far not reach the material quality that is necessary for III-N-technology. In this contribution, exceptional structural quality of Al1-xScxN grown by sputter epitaxy onto GaN is demonstrated, featuring an out-of-plane mosaicity of just 258 arcsec - comparable to state of the art MOCVD and molecular beam epitaxy (MBE) processes. Furthermore, ferroelectric switching is observed in typically non-ferroelectric binary AlN grown by both sputtering and MOCVD onto GaN. Thus, two promising approaches to realize ferroelectric III-N heterostructures with high-throughput methods exist: lattice-matched sputtering of Al1-xScxN on GaN and MOCVD-growth of binary AlN on GaN.