Ternary Alloy Rare-Earth Scandate as Dielectric for $\beta$ -Ga2O3 MOS Structures

A ternary alloy rare-earth scandate, (Y
_0.6
Sc
_0.4
)
₂
O
₃
, is demonstrated as a high-k dielectric insulator for β-Ga
₂
O
₃
MOS devices. (Y
_0.6
Sc
_0.4
)
₂
O
₃
/β-Ga
₂
O
₃
(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 lightemitting diode (LED), demonstrating a peak D
_it
value of 4×10
¹²
cm
^-2
eV
^-1
near the conduction band, and dropping to below 2 × 10
¹¹
cm
^-2
eV
^-1
at 0.9 eV below the conduction band. A total interface charge of <;1 × 10
¹²
cm
^-2
was calculated based on the experimental data. Similar Dit 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 (Y
_0.6
Sc
_0.4
)
₂
O
₃
and low depletion leakage current limited by the generation of holes from deep-level β-Ga
₂
O
₃
traps. High breakdown fields of 4.3-6.0 MV · cm
^-1
were observed. The low Dit value shows the excellent potential of (Y
_0.6
Sc
_0.4
)
₂
O
₃
as a gate dielectric for β-Ga
₂
O
₃
metal-oxide-semiconductor field-effect transistors (MOSFETs).