Design And Implementation Of Field-effect Phototransistors Based On Graphene-quantum Dot Hybrids

Semiconductor quantum dot field effect phototransistors?Q-FET?have attracted much interest in electronics and optoelectronics field,due to their flexibility,low cost,easy fabrication,low energy-consumption and easy integration.Graphene material has an important application in solar cells,light emitting diodes,and field-effect transistors,due to the high carrier mobility?200,000 cm²/?V·s??,good transparency and excellent mechanical properties,including large flexibility and high strength.The photoelectrical characteristics of field-effect phototransistors were investigated experimentally based on a graphene–quantum dot hybrid.The device presented both high emitting efficiency,good photosensitivity of quantum dot and high carrier mobility good transparency of graphene at room temperature.1.In this work,colloidal PbS Q-FETs were successfully fabricated by reasonable structure design and layer-by-layer deposition technique quantum dots.The bipolar property was demonstrated by the output and transfer characteristics,as devices work in I and ? quadrants simultaneously.The mobilities of electron and hole were ?e = 0.16 cm²/?V·s?and ?h = 0.28 cm²/?V·s?,respectively.Quantum dot field effect phototransistors worked as photoconductive detectors at both positive and negative gate bias voltages.2.Under constant gate bias,photocurrent increased exponentially with the intensity of light.The responding region consisted with the absorption range of quantum dots.On this basis,we designed two devices of different structures by chemical vapor deposition method to obtain graphene and transferred it onto Si/SiO₂ substrate.Device 1 comprised two different sizes of PbSe quantum dots in quantum dot layer,while device 2 comprised only one type PbSe quantum dots in quantum dot layer.Two devices had bipolar property at room temperature.The mobilities for electrons and holes were ?e = 98.96 cm²/?V·s?and ?h = 64.56 cm²/?V·s?in the devise 1 and ?e = 1621.0 cm²/?V·s?and ?h = 1228.0 cm²/?V·s?in the devise 2.Both devises exhibited good photoresponse in the NIR region and high responsivities which responsivities up to 0.1 A/W and 1 A/W,respectively.We tested devices the response of different wavelengths for the first time,and get continuous light response current value.The results showed that the photocurrent peak corresponded to the absorption peak of quantum dots.