Al2O3/ $\beta $ -Ga2O3(-201) Interface Improvement Through Piranha Pretreatment and Postdeposition Annealing

In this letter, we report on the improvement of atomic layer deposited (ALD) Al
₂
O
₃
/
$\beta $
–Ga
₂
O
₃
(-201) interface quality through piranha pretreatment and postdeposition annealing (PDA). The high quality interface is verified via the temperature dependent capacitance–voltage (
$C$
–
$V$
) and photo-assisted (deep UV)
$C$
–
$V$
measurements, considering its ultra wide bandgap of 4.8 eV for
$\beta $
-Ga
₂
O
₃
. A low
$C$
–
$V$
hysteresis of 0.1 V from the measurement frequency of 1 kHz to 1 MHz is obtained, compared with the hysteresis of 0.45 V without piranha optimization. An average interface trap density
$({\mathrm{ D}}_{\mathrm {it}})$
of
$2.3 \times 10^{11}$
cm
$^{\mathrm {-2}}\cdot $
eV
$^{\mathrm {-1}}$
is extracted from the photo
$C$
–
$V$
measurements. Piranha pretreatments and PDA turn out to be an effective way to improve the ALD Al
₂
O
₃
/
$\beta $
–Ga
₂
O
₃
(-201) interface for future high quality Ga
₂
O
₃
metal–oxide–semiconductor field-effect transistors.