Epitaxial ScAIN grown by molecular beam epitaxy on GaN and SiC substrates

摘要

Sc_xAl_(1-x)N is a promising ultra-wide bandgap material with a variety of potential applications in electronic, optoelectronic, and acoustoelectric devices related to its large piezoelectric and sponta-neous polarization coefficients. We demonstrate growth of Sc_xAl_(1-x)N on GaN and SiC substrates using plasma-assisted molecular beam epitaxy with χ = 0.14-0.24. For metal-rich growth condi-tions, mixed cubic and wurtzite phases formed, while excellent film quality was demonstrated under N-rich growth conditions at temperatures between 520 and 730 ℃. An rms roughness as low as 0.7 nm and 0002 rocking curve full-width at half maximum as low as 265 arc sec were measured for a Sc_(0.16)Al_(0.84)N film on GaN. To further demonstrate the quality of the ScAlN material, a high-electron-mobility transistor heterostructure with a Sc_(0.14)Al_(0.86)N barrier, GaN/AlN interlayers, and a GaN buffer was grown on SiC, which showed the presence of a two-dimensional electron gas with a sheet charge density of 3.4 × 10~(13)cm~(-2) and a Hall mobility of 910cm~2/V·s, resulting in a low sheet resistance of 213 Ω/□.