Characterization of carbon nanotube film-silicon Schottky barrier photodetectors
(Color online) (a) Schematic of the CNT film-Si Schottky barrier device showing both the top and cross-sectional views. The CNT film is ∼50 nm thick, 400 nm SiO2 is thermally grown on Si, and the metal contact ring is Cr/Pd (10/90 nm). (b) AFM image of a ∼50 nm thick CNT film on SiO2. (c) The photoresponse and noise measurement setup and circuit diagram.
(Color online) (a) Dark I-V characteristics of a CNT film-Si device with a contact area of 500 × 500 μm2 in the bias range from −3 to 3 V at room temperature. (b) Current of the CNT film-Si device as a function of reverse bias voltage in the dark and under λ = 633 nm He–Ne laser illumination. (c) Seven cycles of the photocurrent response when the device is reverse biased at 1 V and is illuminated by a monochromator with a chopped tungsten bromine light source. The output wavelength of the monochromator is selected at 633 nm with a power density of 65 μW/cm2. The chopper frequency is selected to be ∼12 Hz.
(Color online) (a) Zoom-in of a single response cycle of the CNT film-Si photodetector from Fig. 2(c). (b) Spectral responsivity of CNT film-Si and Ti/Au-Si metal control devices (at a reverse bias of 1 V) for several wavelengths in the visible and near infrared regions. The solid lines are a guide for the eye and the dotted lines indicate various external quantum efficiency (QE) values.
(Color online) (a) Current noise spectral density of the CNT film-Si device measured at five different reverse biases ranging from 0.46 to 2.85 V, showing that the noise is 1/f limited. (b) Comparison of the current noise spectral density at 10 Hz for the CNT film-Si and Ti/Au–Si metal control devices as a function of reverse bias current. The dashed lines show the power-law fits, where the extracted exponents are 1.75 and 1.80 for the CNT film and metal control devices, respectively.
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