A single crystalline thin film of Ge on glass is fabricated using wafer bonding and smart cut. A simple metal-insulator-semiconductor detector is demonstrated for visible light and telecommunication wavelength. The implantation damage of separated Ge film bonded on glass is removed by chemical etching, and the surface roughness is reduced from 14to4nm. The defect removal reduces the dark current by a factor of 30 and increases the responsivity by a factor of 1.85 at visible wavelength. The responsivity of 0.27A∕W at 1.3μm wavelength for an unetched device does not increase after damage removal due to the decrease of the absorption layer thickness.

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The Ge-on-insulator metal-oxide-semiconductor detector was fabricated by the wafer bonding and smart-cut. The surface roughness after smart-cut is reduced to be ~7 nm at 150ºC, due to the suppression of hydrogen outdiffusion. The large work function metal (Pt) is used for the gate electrode on the n- type Ge on insulator to reduce the dark current. Due to the small bandgap of Ge, the 850 nm, 1.3 μm and 1.55 μm infrared can be detected. The increasing photo response of the detector using the Ge-on-insulator with decreasing bonding temperature also indicates that the defects caused by hydrogen implantation are passivated more effectively by hydrogen at lower temperature. In order to increase the responsivity of 1.3 μm infrared, n-Ge thickness of 1.3 μm is used, and the responsivity reaches 231 mA/W. The external mechanical strain can further enhance the photo current without degradation of dark current.

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