Investigation of growth parameters for ScAlN-barrier HEMT structures by plasma-assisted MBE

Due to its outstanding polarization properties and the possibility of lattice-matched growth on GaN, Sc x Al 1-x N is a promising material among group III nitrides providing a wide field of potential applications in modern semiconductor technology. However, epitaxial growth of Sc x Al 1-x N by MBE is still in an early stage of research. In this work, Sc x Al 1-x N samples were grown by plasma-assisted MBE on GaN-on-sapphire templates under a variety of growth conditions and pulsed supply of Sc and Al, resulting in compositions ranging from Sc 0.02 Al 0.98 N to Sc 0.69 Al 0.31 N. Samples grown in the highly metal-rich regime showed phase degradation and high surface roughness, whereas growth in the N-rich and intermediate regime led to phase purity and surface roughness as low as 0.7 nm. Electrical characterization revealed a 2DEG for Sc 0.2 Al 0.8 N with a sheet resistance of 215 Ω/□, a Hall mobility of 553 cm 2 V −1 ·s −1 , and a sheet carrier density of 5.26 × 10 13 cm −2 at 77 K.