Sub-60 mV/dec Germanium Nanowire Field-Effect Transistors with 2-nm-thick Ferroelectric Hf0.5Zr0.5O2

We report an n-type Ge nanowire ferroelectric-Hf
0.5
Zr
0.5
O
2
field effect transistor (Ge NW FE-HZO FET) was experimentally demonstrated. An in-situ ALD O
3
treatment was carried out to form an atomically-thin (~0.4 nm) interfacial layer (IL) of GeO
x
, followed by a 2-nm FE-HZO capped with a 1-nm Al
2
O
3
layer. It is found that microwave annealing (MWA) sample shows better uniformity of FE-HZO properties compared to rapid thermal annealing (RTA). The fabricated Ge NW FE-HZO FET shows minimum subthreshold slope (SS
min
) of 55 mV/decade and I
ON
/I
OFF
ratio of 8.1 × 10
⁴
with low hysteresis (30 mV) at drain voltage (V
D
) of 0.1 V.