Ion Irradiation-Induced Interface Mixing and the Charge Trap Profiles Investigated by In Situ Electrical Measurements in Pt/Al2O3/ β-Ga2O3 MOSCAPs

In situ
${I} - {V}$
and
${C}\!\!-\!\!{V}$
measurements were performed during the 120 MeV Au
$^{9+}$
ion irradiation on the Pt/Al
$_{{2}}\text{O}_{{3}}/\beta $
-Ga
₂
O
₃
, metal–oxide–semiconductor capacitors (MOSCAPs), to comprehend the swift heavy ion (SHI)-induced effects at the interface and in the device performance. At a maximum fluence of
$2\times 10^{{12}}$
ions/cm
²
, the
${I}-\!{V}$
data showed a rise in the reverse leakage current by four orders of magnitude compared to the pristine device. The trap level (below the conduction band of Al
₂
O
₃₎
from Poole–Frenkel emission exhibits a variation from
$\sim $
1.1 to 0.91 eV. The conduction band offset
${(\phi }_{B}{) }$
of Al
$_{{2}}\text{O}_{{3}}/\beta $
-Ga
₂
O
₃
changes from 1.48 to 1.25 eV as estimated under the Fowler–Nordheim tunneling mechanism. In situ
${C}\!\!-\!\!{V}$
measurements show a significant shift in the flat band voltages and increased oxide in the border and interface due to charge trapping. The X-ray photoelectron spectroscopy (XPS) measurements of Al 2p and O 1s core levels revealed the pre-existing oxygen defects in Al
₂
O
₃
, which increase with fluence. The deconvoluted peaks of Al 2p at 74.6 eV designated to Al-sub oxide and the O 1s peak variation in the FWHM signifies the increase in the O defects. Cross-sectional transmission electron microscopy (XTEM) measurements on the irradiated device (at
$2\times 10^{{12}}$
ions/cm
$^{{2}}{)}$
revealed a modulated interface of Al
$_{{2}}\text{O}_{{3}}/\beta $
-Ga
₂
O
₃
and the formation of an interlayer of
$\sim $
4 nm Al
_x
Ga
_y
O
_z
. The scanning transmission electron microscope (STEM)-based high-angle annular dark-field imaging (HAADF) energy-dispersive X-ray spectroscopy (EDS) mapping revelation and the depth profiles of XPS data confirm the formation of an Al
_x
Ga
_y
O
_z
interlayer.