Device Physics On Colloidal Quantum Dots Short Wavelength Infrared Photodetectors

Short-wave infrared(SWIR)is an electromagnetic wave with wavelength between0.76?2.5 ?m,with strong atmospheric transmission and capacity for material authentication.Hence,SWIR imaging shows a wide range of applications in military,industrial,agricultural,and medical fields.The traditional SWIR cameras have excellent performance,but their manufacturing cost is very high,hindering the wide-scale popularization of SWIR imaging.Seeking for materials that can realize low-cost and high-performance SWIR imaging is a research hotspot in recent years.Colloidal quantum dot(CQD)is a kind of inorganic semiconductor nanocrystals with the size smaller than the exciton Bohr radius of the host material.Due to quantum confinement effect,the optical and electronic properties of CQD are tunable through adjusting the size.Lead sulfide(Pb S)CQD is a mature SWIR absorption material with excellent photoelectric properties.The major of studies have been focused on Pb S CQD solar cell for many years.However,there are few studies reported on Pb S CQD SWIR photodetectors,especially on device physics.The main research contents of this paper are as follows:1.The physical mechanism of dark current,quantum efficiency,noise,and response ate of the Pb S CQD photodiode were introduced.And based on the device design hrough simulation,the influence of key parameters on the device performance ere studied.2.The comprehensive photoelectric properties of halogen passivated Pb S CQD thin ilm were measured,including complex refractive index,dielectric constant, absorption coefficient,mobility,conductivity,doping concentration,defect depth and concentration,etc.And the corresponding database is set up3.Pb S CQD SWIR photodetectors with different structures were fabricated and characterized and the device physics was in detail studied.?In conclusion,the dark current is mainly attributed to the generation current caused by bulk defects and the trap assisted tunneling current caused by interface defects.The loss of external quantum efficiency is mainly resulted from the optical loss under large bias and the carrier recombination loss under small bias.The response time is mainly limited by the low mobility of Pb S CQD,which leads to a long drift time of carriers in the depletion region.