High-density two-dimensional electron gas in ScAlN/GaN heterostructures grown by sputter epitaxy with enhanced metal supply

Abstract We report high-density two-dimensional electron gases in ScAlN/AlGaN/AlN/GaN heterostructures grown by sputter epitaxy with an enhanced metal supply. By optimizing the growth temperature to 775 °C, we achieved atomically flat surfaces and high crystallinity. Moreover, we obtained a record-high sheet carrier density ( n s ) of 2.24 × 10 13 cm −2 for the sputtered ScAlN films, which is comparable to the values achieved using metal–organic chemical vapor deposition and molecular beam epitaxy. Temperature-dependent Hall effect measurements and scattering analysis using Matthiessen’s rule revealed that the high carrier density enhances interface roughness scattering, which becomes the dominant mobility-limiting mechanism at low temperatures. These results demonstrate that sputter epitaxy with an increased metal-to-nitrogen flux ratio enables high-density polarization-induced 2DEGs and provides a competitive approach for realizing high-performance ScAlN/GaN HEMT heterostructures.