Study On Flexible Graphene Field Effect Transistor With High On/off Ratio

Field-effect transistors are important components in the field of semiconductor devices and integrated circuit research.With the development of Moore's Law,silicon-based field-effect transistors have been scaling down in size and are gradually approaching their physical limits,while two-dimensional semiconductor materials such as graphene and molybdenum disulfide,due to their excellent physical and chemical properties,are expected to become the channel material of a new generation of field-effect transistors,which has attracted widespread attention in the field of electronic information.In particular,graphene,with its ultra-high carrier mobility and mechanical flexibility,has made field-effect transistors and flexible electronic devices using graphene as a channel material become a research hotspot in recent years.However,the traditional gate dielectric has a weak ability to control the carriers of twodimensional semiconductor materials,which makes graphene field-effect transistors require a large operating voltage.Therefore,it is necessary to develop new dielectric materials to improve the gate control ability of transistors.Also,graphene has the characteristics of no band gap,which severely limits the practical application of graphene field effect transistors.Especially when a high on/off ratio of the transistor is required,the problem of band gap regulation of graphene needs to be solved urgently.In this paper,ionic liquid is selected for the preparation of gate dielectric materials,and a flexible graphene field-effect transistor with high on-off ratio and adjustable on-off ratio has been developed.The main research contents and results are as follows:First,the electrical properties of ionic liquid gated graphene field effect transistors and ionic liquid gated molybdenum disulfide field effect transistors are studied;the study found that ionic liquids can greatly improve the current density of graphene field effect transistors and molybdenum disulfide field effect transistors,has a strong carrier control effect on the channel material,and the improvement of the device gate control ability is realized;the transistor can be switched in the range of ±1 V;the threshold voltage and sub-threshold swing amplitude are significantly reduced in the ionic liquid gated molybdenum disulfide field effect transistor;Second,a method of making ionic liquid into ionic gel as the transistor gate dielectric is proposed,and ionic gel gated graphene field effect transistors have been developed;research has found that the ion gel gate makes the gate control ability more effective in graphene field effect transistors,has improved the current density,and the on/off ratio has been significantly increased to around 6;Third,a flexible graphene field-effect transistor with ion gel as the gate dielectric was developed;the study found that the device characteristics can be maintained in a relatively stable state within 15 % of the bending degree,because both graphene and ion gel films have good mechanical flexibility;the effect of rapid thermal annealing process on the contact performance of the device is studied;the research found that when the rapid annealing temperature is 300 ?,the contact performance of graphene and the metal electrode is significantly improved,and the on/off ratio of the transistor reaches its highest value.Fourth,the development of flexible graphene field-effect transistors with high on/off ratio is studied;the research found that when flexible graphene field-effect transistors work under bending conditions,as the degree of bending increases,the on/off ratio first decreases slightly,and then increases rapidly.When a bending of 8.1% is applied,the on/off ratio reaches about 400,which is much higher than that of silicon-based graphene field effect transistors,and a flexible graphene field effect transistor with adjustable on/off ratio is realized.