Ternary Alloy Rare-Earth Scandate as Dielectric for β-Ga2O3 MOS Structures

A ternary alloy rare-earth scandate, (Y0.6Sc0.4)(2)O-3, is demonstrated as a high-k dielectric insulator for beta-Ga2O3 MOS devices. (Y0.6Sc0.4)(2)O-3/beta-Ga2O3 (010) MOS capacitors were fabricated and characterized using capacitance-voltage (C-V) techniques and interface state density (D-it) methods. The D-it distribution was extracted using photo-assisted C-V with a 265-nm light-emitting diode (LED), demonstrating a peak D-it value of 4x10(12) cm(-2) eV(-1) near the conduction band, and dropping to below 2x10(11) cm(-2) eV(-1) at 0.9 eV below the conduction band. A total interface charge of <1 x 10(12) cm(-2) was calculated based on the experimental data. Similar D-it values were observed using the Terman method for the energy range 0.35-0.55 eV below the conduction band. Current-voltage (J-V) measurements showed rising accumulation leakage current due to bulk-limited transport of electrons through traps in the (Y0.6Sc0.4)(2)O-3 and low depletion leakage current limited by the generation of holes from deep-level beta-Ga2O3 traps. High breakdown fields of 4.3-6.0 MV . cm(-1) were observed. The low Dit value shows the excellent potential of (Y0.6Sc0.4)(2)O-3 as a gate dielectric for beta-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs).