| Compared with the traditional switch,the photoconductive switch(PCSS)has a great advantage,the response speed is quite fast,the response time in the picosecond(ps)magnitude,high pressure resistance,and has a surprising feature is good optical isolation characteristics and not electromagnetic Interference characteristics,although the photoconductive switch has a great advantage,but there are some shortcomings,such as the actual withstand voltage of photoconductive switch is often lower than the theoretical withstand voltage,and the device leakage current is too large and so on.Based on Si C-PCSS also has such a problem.In this paper,Al N passivation layer is deposited on the surface of the photoconductive switch substrate to perform surface passivation,which improves the working performance of the photoconductive switch.In this paper,a photoconductive switch(PCSS)device model is established based on the drift-diffusion theory.The model is made of vanadium-doped semi-insulating n-type 4H-Si C.The device structure is electrode coplanar type,The width of the transverse direction is 150μm,the longitudinal thickness is 15μm,and the width of the electrode is 30μm.This paper mainly studies the performance change of the photoconductive switch,and deposits an Al N passivation layer on the 4H-Si C substrate.The research work is divided into the following parts:(1)The effect of the incorporation of vanadium into the Si C substrate as a deep level trap and the trap concentration on the impurity of the shallow level in Si C was investigated.In this paper,the trap concentration is 1×1016/cm3,1×1017/cm3,1×1018/cm3,The results show that the photocurrent and dark current decrease obviously when the trap is added,and the leakage current of the decreases,With the increase of the trap concentration,the dark resistivity increases,When the trap concentration reached 1×1018cm3,almost all free electrons were ionized from unintentionally doped superficial impurity N(concentration 3×1015/cm3).and the deep impurity vanadium plays a good compensating effect.So,the deep impurity vanadium plays a good compensating effect.And the trap concentration was chosen Depending on the concentration of the unintentionally doped superficial impurity in the Si C material.(2)The dark state characteristics of Si C-PCSS before and after the deposition of Al N passivation layer on 4H-Si C surface were studied.The results show that after the passivation treatment,the dark current can be effectively reduced,the dark current is significantly reduced,the leakage current is prevented from being too large,and the dark state characteristic of Si C-PCSS can be improved.(3)The effect of Al N passivation layer thickness and surface area on the properties of Si C-PCSS was studied.The thickness of Al N passivation layer was 0.5μm,1.0μm and 2.0μm respectively.The surface area was set by changing the length of Al N passivation layer,Respectively,50μm,70μm,90μm,the results show that the deposition of Al N passivation layer thickness is not thicker the better,the need to deposit a thin layer of Al N passivation layer,Al N thickness of 0.5μm and the length of 90μm The current drop is more obvious,it can be obtained when the passivation layer with Al N passivation in addition to all the other regions,the passivation effect can be optimal.(4)The breakdown characteristics of the Al N passivation layer on the surface of 4H-Si C were investigated.The results show that a thin layer of Al N passivation layer on the surface of 4H-Si C can improve the breakdown voltage of Si C-PCSS with the breakdown voltage of about 7.5KV.(5)The process of making Si C-PCSS is studied,and the concrete preparation process of transverse structure Si C-PCSS is designed,which is fully prepared for the production of light guide switch.In this paper,the properties of Si C-PCSS were changed by depositing a thin layer of Al N passivation layer on the surface of 4H-Si C substrate.The results obtained from the above research work were as follows: The addition of Al N to other regions outside the electrode region can not only change the dark state characteristics of Si C-PCSS,but also improve the withstand voltage of Si C-PCSS. |
