Graphene/Semiconductor Photodetectors Prepared by Molecular Beam Epitaxy

Through the attachment of mono-layer graphene films to either GaAs substrates or epi-wafers prepared by the molecular beam epitaxy (MBE), high-responsivity graphene/semiconductor photodetectors can be fabricated. For the graphene/undoped GaAs device, responsivity values up to 102kA/W are observed in the 750-850 nm wavelength range. To further extend the detection wavelengths, the other sample with 10 nm In0.15Ga0.85As grown on undoped GaAs substrates is prepared by using MBE. Besides high responsivity values, the detection wavelengths are extended from 900 to 1000 nm. By using the sample with 2.4 mono-layer (ML) InAs quantum dots (QDs) as the light absorption layer, the device has demonstrated an even longer detection wavelength 1200 nm. The observation of high responsivities for devices with graphene on either bulk semiconductors or epi-wafers prepared by MBE has demonstrated the potential of such devices in practical applications.