Kavli Affiliate: David A. Muller
| First 5 Authors: Thai-Son Nguyen, Naomi Pieczulewsi, Chandrashekhar Savant, Joshua J. P. Cooper, Joseph Casamento
| Summary:
AlScN is a new wide bandgap, high-k, ferroelectric material for RF, memory,
and power applications. Successful integration of high quality AlScN with GaN
in epitaxial layer stacks depends strongly on the ability to control lattice
parameters and surface or interface through growth. This study investigates the
molecular beam epitaxy growth and transport properties of AlScN/GaN multilayer
heterostructures. Single layer Al$_{1-x}$Sc$_x$N/GaN heterostructures exhibited
lattice-matched composition within $x$ = 0.09 — 0.11 using substrate
(thermocouple) growth temperatures between 330 $ ^circ$C and 630 $ ^circ$C.
By targeting the lattice-matched Sc composition, pseudomorphic AlScN/GaN
multilayer structures with ten and twenty periods were achieved, exhibiting
excellent structural and interface properties as confirmed by X-ray diffraction
(XRD) and scanning transmission electron microscopy (STEM). These multilayer
heterostructures exhibited substantial polarization-induced net mobile charge
densities of up to 8.24 $times$ 10$^{14}$/cm$^2$ for twenty channels. The
sheet density scales with the number of AlScN/GaN periods. By identifying
lattice-matched growth condition and using it to generate multiple conductive
channels, this work enhances our understanding of the AlScN/GaN material
platform.
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