Study On Lateral Photovoltaic Properties Of MSe_x(M=Sn,Mo,W)/Si Heterostructures

Lateral photovoltaic effect(LPE)is one kind of photovoltaic effect.It has a good application prospect in the photoelectric detection and position sensitive detectors(PSDs).Many scientific reserchers pay attention to LPE.So it is necessary to figure out it's sources and influencing factors.Transition-metal dichalcogenide has many excellent properties.Se based semiconductors han good photoelectric properties with two-dimensional layered structure.We choose it as the materals to research LPEThe film was grown by PLD method on Si substrate and we study it's structure and LPE properties to figure out it's influencing factors.The main research content is as follows:First,we use pulse laser deposition(PLD)to grow SnSe films on Si substrates.Its structure and element analysis show that we have successfully developed high quality SnSe films.The longitudinal I-V tests show that the heterojunction formed strength of unidirectional conductivity and structure,which is conducive to the vertical separation of photogenerated carrier.On the SnSe film surface,we obtained the 350 mV/mm position sensitivity and 25 ?s photovoltaic recovery time.And we can get a very fast recovery time of 2?s by changing the circuit resistance.The change of the wavelength and power of the side photovoltaic with different thickness of the heterojunction shows that the side photovoltaic mainly comes from the photoelectric effect of heterojunction rather than the thermal effect.In the nonlinear I-V curve surface test of SnSe films show that in the SnSe and p-Si interface is formed between the inversion layer with high mobility,which is conducive to the photocarrier horizontal diffusion along the surface of SnSe film,so that the SnSe/Si heterojunction with ultrafast photoelectric response recovery.Second,we use pulse laser deposition(PLD)to grow N type MoSe2 films on Si substrates.XRD shows that the film has an epitaxial structure and longitudinal I-V test shows that the formation of strength of inner unidirectional conductivity of heterojunction,which is conducive to the vertical separation of photogenerated carrier.The 450 mV/mm position sensitivity and the 45 ?s photovoltaic recovery response were obtained on the MoSe2 film surface.By changing the external resistance of the circuit,we obtained an ultrafast time response of 2.5 ?s.The change of the wavelength and power of the side photovoltaic with different thickness heterojunction shows that the main reason for the lateral photovoltaic is the photoelectric effect of heterojunction.In the nonlinear I-V surface test of MoSe2 films show that in the MoSe2 and Si interface is formed between the inversion layer has a high mobility which is conducive to the photocarrier horizontal diffusion along the surface of MoSe2 film,so that the MoSe2/Si heterojunction with ultrafast photoelectric response recovery.MoSe2 and Si heterostructure N type semiconductor structure with lateral photovoltaic effect is higher than the SnSe/Si heterojunction,but the recovery of two photoelectric response time is basically the same,which further verified the Si film and the substrate between the inversion layer formed on the lateral photovoltaic effect of ultrafast response time plays a crucial role.Finally,N type semiconductor material WSe2 film was grown on Si substrate by pulse laser deposition(PLD).The XRD test data show that the films have epitaxial structure.The test results show that the longitudinal I-V heterojunction WSe2 and Si substrate with one-way guide formed in common and built electric field,which is conducive to the vertical separation of photogenerated carrier.On the WSe2 film surface,we obtain the sensitivity of the 200 mV/mm position and the ultrafast time response of 0.6 ?s,and change the external resistance of the circuit,which is basically unchanged.The lateral photovoltaic of heterogeneous heterojunctions with different laser wavelengths shows that the photovoltaic effect is mainly attributed to the photoelectric effect of heterojunction in this structure.The I-V curves on the surface of WSe2 films show that the inversion layer structure between WSe2 and Si interfaces is not effective.Because WSe2 material has electron mobility of up to 705 cm2·V-1·s-1,it is much higher than the former two materials,so it is very favorable for the diffusion of photogenerated carriers and thus has very fast photoelectric recovery response.Heterostructure N type semiconductor WSe2 /Si junction is faster than SnSe/Si and MoSe2/Si structure of photoelectric response recovery,this is due to its high electron mobility what makes the photogenerated electrons no longer migrate from the inversion layer,it also shows that the use of high carrier mobility material consisting of a heterojunction can generate ultrafast time response.