Self-organized gate stack of Ge nanosphere/SiO2/Si1-xGex enables Ge-based monolithically-integrated electronics and photonics on Si platform

We report the first-of-its-kind, self-organized gate stack of Ge nanosphere (NP) gate/SiO
₂
/Si
_1-x
Ge
_x
channel fabricated in a single oxidation step. Process-controlled tunability of the Ge NP size (5-90nm), SiO
₂
thickness (2-4nm), and Ge content (x = 0.65-0.85) and strain engineering (ε
_comp
= 1-3%) of the Si
_1-x
Ge
_x
are achieved. We demonstrated Ge junctionless (JL) n-FETs and photoMOSFETs (PTs) as amplifier and photodetector, respectively, for Ge receivers. L
_G
of 75nm JL n-FETs feature I
_ON
/I
_OFF
> 5×10
⁸
, I
_ON
> 500μA/μm at V
_DS
= 1V, T= 80K. Ge-PTs exhibit superior photoresponsivity >1,000A/W and current gain linearity ranging from nW-mW for 850nm illumination. Size-tunable photo-luminescence (PL) of 300-1600nm (NUV-NIR) are observed on 5-100nm Ge NPs. Our gate stack of Ge NP/SiO
₂
/Si
_1-x
Ge
_x
enables a practically achievable building block for monolithically-integrated Ge electronic and photonic ICs (EPICs) on Si.