Very large photoresponsiviy and high photocurrent linearity for Ge-dot/SiO₂/SiGe photoMOSFETs under gate modulation

We report a novel visible−near infrared photoMOSFET containing a self-organized, gate-stacking heterostructure of SiO₂/Ge-dot/SiO₂/SiGe-channel on Si substrate that is simultaneously fabricated in a single oxidation step. Our typical photoMOSFETs exhibit very large photoresponsivity of 1000−3000A/W at low optical power (< 0.1μW) or large photocurrent gain of 10³−10⁸A/A with a wide dynamic power range of at least 6 orders of magnitude (nW−mW) linearity at 400−1250 nm illumination, depending on whether the photoMOSFET operates at V_G = + 3− + 4.5V or −1− + 1V. Numerical simulations reveal that photocarrier confinement within the Ge dots and the SiGe channel modifies the oxide field and the surface potential of SiGe, significantly increasing photocurrent and improving linearity.