Fabrication And Photoelectric Properties Of PbSe/MoSe₂ Heterojunction

As a narrow band gap semiconductor with direct band gap,PbSe has important value in infrared detection.However,the photoelectric properties of PbSe film are seriously affected by its low carrier mobility and carrier recombination.The photoelectric properties can be improved to some extent by sensitization,but still has great limitations.In recent years,following graphene,two-dimensional chalcogenide semiconductors represented by MoSe₂ have received widespread attention.Although MoSe₂ and PbSe have different crystal structures and their lattice constants are also different,due to the van der Waals force between layers of MoSe₂,it is possible to epitaxially grow high-quality PbSe thin films on the surface of MoSe₂.The PbSe/MoSe₂ heterojunction photodiode shows a new method for the infrared detection application of PbSe thin films.To this end,the paper has carried out the following research work:Firstly,PbSe thin films were grown by molecular beam epitaxy.X-ray diffraction?XRD?,scanning electron microscopy?SEM?and X-ray photoelectron spectroscopy?XPS?were used to characterize the grown PbSe films.The grown film has a single?100?orientation,and the film has a high crystal quality.On this basis,the paper further studied the effect of sensitization on the photoelectric response of the grown PbSe film.The results show that the photodetector fabricated by pristine PbSe film has greater dark current and photocurrent.Under the 1300 nm radiation,the responsivity and detectivity of devices are 53 mA/W and 1.7×10⁹ Jones,respectively.The sensitization process reduces the photocurrent and dark current of the device,but the light-dark current ratio is higher.The responsivity and detectivity of short-wave infrared light of 1300 nm are 36mA/W and 3.3×10⁹ Jones,respectively.Although the responsivity is reduced,the detectivity is increased by 2 times.Secondly,the paper studied the growth of MoSe₂ thin films by molecular beam epitaxy.The MoSe₂ thin films was characterized by Raman,XPS and SEM.The characterization results showed that when the substrate temperature was 700°C and the evaporation temperature of Se source was 160°C,the deposited MoSe₂ film is a few layers of two-dimensional material with good quality,and has excellent photoelectric properties.On this basis,high-quality MoSe₂ film was grown on the surface of SiO₂/Si substrate and then PbSe film was grown in situ to fabricate PbSe/MoSe₂ heterojunction material by the optimized growth conditions.And fabricated a photodiode based on PbSe/MoSe₂ heterojunction.The performance shows that the diode has good rectification effect and excellent photoelectric properties.Under the 1300 nm radiation,the photodiode has significant photocurrent at zero bias,which confirms the photo-generated carrier separation effect at the PbSe/MoSe₂ heterojunction interface.The detectivity of the diode can reach 1.6×10¹⁰ Jones and 1.1×10¹¹ Jones under zero bias and-5 V bias,respectively.The detectivity is 33 times higher than that of the photoconductive detector fabricated by the sensitized PbSe film.It provides another technical route for infrared detection applications of PbSe films.For comparison,the paper studied the structure of PbSe/MoSe₂ heterojunction photodiode.PbSe film was deposited on the surface of SiO₂/Si substrate,and then MoSe₂film was deposited on the surface of PbSe film to fabricate photodiode based on MoSe₂/PbSe heterojunction.Under the 1300 nm radiation,the detectivity of the photodiode is 3.8×10⁹ Jones and 5.2×10⁹ Jones under zero bias and-5 V bias,respectively.Compared with the PbSe/MoSe₂ heterojunction photodiode,the overall performance of the device is greatly reduced,which should be related to the quality of the PbSe and MoSe₂ film grown on the surface of the SiO₂/Si substrate.Therefore,the results indicate the direction of optimization of PbSe/MoSe₂ heterojunction photodiode.