High-Performance Ge nMOSFETs With $\hbox{n}^{+}\hbox{-} \hbox{p}$ Junctions Formed by “Spin-On Dopant”

We report high-mobility Ge nMOSFETs using a simple approach to form n
⁺
-p junctions by rapid thermal diffusion of "spin-on dopant" to avoid implantation damage. These junctions show a high I
_ON
/I
_OFF
ratio (~10
⁵
-10
⁶
) and an ideality factor of ~1.03, indicating a low defect density in the junction, whereas ion-implanted junctions show higher /off (by approximately one to two orders) and a larger ideality factor (n ~ 1.45). Germanium (100) nMOSFETs with diffusion doping and GeO
₂
passivation show a high I
_ON
/I
_OFF
ratio of ~10
⁴
-10
⁵
, a low SS of 111 mV/decade, and a high μ
_eff
(679 cm
²
· V
^-1
· s
^-1
at peak). The diffusion-doped devices also show lower (approxi mately one order) GIDL and a higher (~1.3×) drive current of ~12 μA/μm in an L ~ 20 μm device at V
_G
- V
_T
= 2 V and V
_D
= 1 V, compared to the implanted devices. Moreover, diffusion-doped Ge (111) devices show even higher μ
_eff
(970 cm
²
· V
^-1
· s
^-1
at peak) and ~1.5× enhancement over the diffusion doped Ge (100) devices and surpass the universal Si mobility at low effective fields.