  Epitaxial Sc$_x$Al$_{1-x}$N thin films of ~100 nm thickness grown on metal
polar GaN exhibit significantly enhanced relative dielectric permittivity
($\epsilon_r$) values relative to AlN. $\epsilon_r$ values of ~17 to 21 for Sc
contents of 17 to 25% (x=0.17 to 0.25) measured electrically by
capacitance-voltage (CV) measurements at 500 kHz frequency indicate
Sc$_x$Al$_{1-x}$N has the largest relative dielectric permittivity of any
existing nitride material. This points toward the usage of Sc$_x$Al$_{1-x}$N as
potential epitaxial, single-crystalline dielectric material that can be
deposited in situ on GaN and AlN electronic and photonic devices for enhanced
performance.
