Impact of Nitrogen Incorporation on the Interface Between Ge and La2O3 or Y2O3 Gate Dielectric: A Study on the Formation of Germanate

La
₂
O
₃
and Y
₂
O
₃
are used as gate dielectric in Ge MOS capacitors, and their electrical and interfacial properties are comparatively studied. Due to the much higher reactivity of La
₂
O
₃
with Ge than Y
₂
O
₃
, thicker germanate interlayer is formed, leading to better interface quality for the former. Moreover, it is found that N incorporation in the oxides reduces the formation of both germanate and GeO
_x
, with much more obvious effect for La
₂
O
₃
and thus the best interface quality (a low interface-state density of 4.96 × 10
¹¹
cm
^-2
eV
^-1
), which gives promising electrical properties: large equivalent dielectric constant (18.8), small flat-band shift (0.37 V), low gate leakage current (2.89 × 10
^-4
A/cm
²
at V
_g
= V
_fb
+ 1 V), and high reliability under electrical stress.