Ferroelectric N-polar ScAlN/GaN heterostructures grown by molecular beam epitaxy

We demonstrate robust ferroelectricity in single-crystalline wurtzite phase N-polar ScAlN/GaN heterostructures grown on on-axis c-plane sapphire substrates by molecular beam epitaxy. The exactly aligned crystallographic orientation among the ScAlN, GaN, and sapphire substrate has been confirmed using x-ray diffraction measurements. The nearly lattice-matched N-polar Sc0.21Al0.79N/GaN heterostructure shows a highly uniform coercive field (similar to 4.6MV/cm at 10kHz) and remnant polarization (similar to 90 mu C/cm(2)) across the whole wafer. The reliability of N-polar Sc0.21Al0.79N/GaN ferroelectricity has been systemically characterized using retention and endurance tests. Both the coercive field and remnant polarization exhibit negligible degradation over 10(5) switching cycles, which is among the best reported for ferroelectric III-nitrides. This work offers a viable path for fully epitaxial heterogeneous integration of ferroelectricity into N-polar III-nitride heterostructures, which, together with the recent demonstration of fully epitaxial ferroelectric metal-polar ScAlN, will find important applications in next-generation high-power and high-frequency electronics, memory electronics, acoustic resonators and filters, optoelectronics, and integrated quantum photonics.

Automated summary

In this study, robust ferroelectricity was demonstrated in single-crystalline thin films. The crystallographic alignment was confirmed using x-ray diffraction measurements. The highly uniform coercive field and remnant polarization were observed in the nearly lattice-matched heterostructure. The reliability of the ferroelectricity was systematically characterized and showed negligible degradation after a large number of switching cycles. This research provides a feasible pathway for fully epitaxial integration of ferroelectricity into nitride heterostructures, with important applications in various fields.