Impact of Postdeposition Annealing Ambient on the Mobility of Ge nMOSFETs With 1-nm EOT Al2O3/GeOx/Ge Gate-Stacks

The impact of postdeposition annealing (PDA) ambient on electrical properties of thin equivalent oxide thickness (EOT) Al
₂
O
₃
/GeO
_x
/Ge gate-stacks is investigated. It is found that the surface states inside the conduction band of Ge are significantly suppressed by 40% through PDA with atomic deuterium ambient. As a result, enhancement of the effective mobility in the Ge nMOSFETs is realized in high normal field region. The electron mobility of 396 cm
²
/Vs is achieved at N
_s
of 10
¹³
cm
^-2
with small EOT of ~1 nm, which is similar to the highest mobility reported so far at such small EOT range.