Epitaxial Sc_xAl_1−xN on GaN exhibits attractive high-K dielectric properties

Epitaxial Sc xAl1− xN thin films of ∼100 nm thickness grown on metal polar GaN substrates are found to exhibit significantly enhanced relative dielectric permittivity (εr) values relative to AlN. εr values of ∼17–21 for Sc mole fractions of 17%–25% ( x = 0.17–0.25) measured electrically by capacitance–voltage measurements indicate that Sc xAl1− xN has the largest relative dielectric permittivity of any existing nitride material. Since epitaxial Sc xAl1− xN layers deposited on GaN also exhibit large polarization discontinuity, the heterojunction can exploit the in situ high-K dielectric property to extend transistor operation for power electronics and high-speed microwave applications.