Research On Vertical Field-effect Phototransistor Based On PbS Quantum Dot

As a new type of photodetector,the field-effect photodetector can increase the conduction current gain by controlling the grid voltage,and has the advantages of strong photoelectric response,large photoelectric gain and high specific detection rate.It has important application prospects in fields such as distance and biological imaging.This thesis proposes a new method for fabricating high-performance vertical fieldeffect phototransistors.Lead sulfide(PbS)quantum dot vertical field-effect phototransistors were prepared using simple semiconductor micro-nanofabrication processes.The device used electrode-patterned ITO/glass as the substrate,poly(methyl methacrylate)(PMMA)as the dielectric layer,PbS quantum dots as the photosensitive channel layer,multi-walled carbon nanotube(MWCNT)films as the intermediate source electrode,and silver electrodes as the drain electrode.The PbS quantum dot material was prepared and characterized,and the average size was determined to be 3 nm,with strong absorption at around 832 nm in the near-infrared region and an absorption edge at around 1100 nm.The PbS film deposited on the MWCNT film was relatively uniform,with a surface roughness of about 0.3 nm.The MWCNT film exhibited smooth and almost flat absorption characteristics,with no specific absorption edge in the range of 300-1000 nm.Considering the trade-off between the conductivity of the MWCNT film and its optical transparency,the bestperformance was achieved when the thickness was about 490 nm,with a conductivity of 3.92×103 S/m.The PbS quantum dot vertical field-effect phototransistor exhibited an output current density of 3 A/cm2 and a switch ratio of about 4.2 at room temperature,with a field-effect hole mobility of 17.1 cm2/V.s.Additionally,the unique properties of the MWCNT porous film provided a high-conductivity network for carrier transfer and separation,resulting in better photoelectric properties.At an illumination intensity of 0.6 μW/cm2@808 nm,a photoresponse rate of 3.16 AW-1 and a specific detectivity of 2.33 × 1012 Jones were achieved,with an external quantum efficiency of about 484.6%.The device exhibited good dynamic response to light signals,with rise and fall times of 31.8 ms and 32.9 ms,respectively.