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, ScxAl1-xN is a promising material among group III nitrides providing a wide field of potential applications in modern semiconductor technology. However, epitaxial growth of ScxAl1-xN by MBE is still in an early stage of research. In this work, ScxAl1-xN 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 Sc0.02Al0.98N to Sc0.69Al0.31N. 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 Sc0.2Al0.8N with a sheet resistance of 215 O/squ, a Hall mobility of 553 cm2 V−1centerdots−1, and a sheet carrier density of 5.26 × 1013 cm−2 at 77 K.