Investigating On The Contact Resistance Of Photosensitive Organic Field-effect Transistor

With the advantages of low cost,low temperature manufacturing,ease of processing,flexibility,photosensitive organic field-effect transistor(PHOFET)has attracted extensively attention.It is the future development direction of the semiconductor devices.However,the performance of PHOFET is limited by the large contact resistance,it is very important to investigate the contact resistance.In this thesis we focus on two kinds of device structures of PHOFET to investigate the contact resistance,which are the bottom gate bottom contact(BGBC)and the bottom gate top contact(BGTC),respectively.In order to investigate the relationship of contact resistance and photosensitivity characteristics on the source/drain contact length,and then extract the contact resistance of BGTC device.On the other hand,it is investigate that how the source/drain contact thickness affect the contact resistance and photosensitivity characteristics,and we extracted the contact resistance of BGBC device.Firstly,the pentacene photosensitive organic field-effect transistor with the BGTC is prepared and the effect of contact length on the photoelectric properties and the extraction of the contact resistance are investigated in the dark and illumination conditions.The result shows that the drain current of the device increase with the contact length and tends to be saturated,and the saturated contact length is 1.2 mm.By analyzing the distribution of the electric field at the source / drain electrode and its effect on the charge transport,we carry out the numerical simulation.The contact resistance is investigated by preparing the devices with different channel length.The result also shows that the contact resistance decreases with the increase of the gate voltage.When the gate voltage is-40 V,the contact resistance is 8.41 × 107?.Secondly,different thickness semiconductor thin films and electrodes have influence on the device performance and photosensitivity characteristics.We investigated the pentacene organic field-effect transistor with the BGBC in detail.The result shows that the contact resistance decreases with the increase of electrode thickness and gate voltage.The thickness of the organic semiconductor film with influence on the device performance and the photosensitive property is investigated.The result shows that the contact resistance decreases with the increase of the pentacene thickness.The photoresponsivity of the device increases with the thickness of the pentacene layer(in the range of 25 nm to 55 nm).