Research On Novel Graphene Radio Frequency Devices And Optoelectronic Integrated Chips

Graphene,a new two-dimensional material,has become a focus in microelectronics and optoelectronics due to its excellent features,such as high carrier mobility,wide spectral response and easily tunable photoelectric response.In this thesis,researches on novel radio frequency(RF)devices based on graphene field-effect transistor(GFET)and graphene photodetector(GPD)and on novel optoelectronic integrated chips based on GPD are shown,which may open up a new prospect for the development of information technology.Firstly,novel buried-gate GFETs and GPDs are investigated.Both graphene-based and heavily doped silicon-based buried-gate techniques are proposed.GFETs applying these novel buried-gate techniques are demonstrated.PN junction-based GPD with tunable photoresponse are achieved by utilizing heavily doped silicon-based buried-gate technique.With these novel buried-gate techniques,the tunable feature of graphene is enhanced without causing additional damage to graphene as in top-gate techniques.Hence,the novel buried-gate technique could be regarded as an excellent platform to improve the performance of graphene devices.Secondly,novel GFET-based frequency multipliers are demonstrated.Frequency triplers and quadruplers are initiatively achieved with a single GFET.Chemical vapor deposition(CVD)grown single-layer graphene with micrometer scale graphene flakes interspersed on the surface is innovatively used to implement FETs for the purpose of frequency tripling.More than 94% of the output RF power is concentrated at desired trebled frequency.To the best of our knowledge,it is the highest output spectral purity for reported frequency triplers.In another work,multi-mode frequency multipliers with tunable multiplication factor are creatively completed by utilizing dual-gated GFETs.In suitable operating regions,dual-gated GFETs can work as high performance frequency doublers,triplers and quadruplers.Thirdly,novel GPD-based photoelectric mixers are studied.A novel GPD with open annular channel are designed and fabricated.Nonlinear optical response is achieved in the GPD.Frequency mixing of two intensity-modulated optical signals in GHz range is performed with nonlinear GPDs.This work opens interesting perspectives in the utilization of GPDs for frequency conversion applications.This new concept of frequency conversion may find its significant roles in the next-generation communication services.In addition,this study experimentally verified the feasibility of using optical signals to modulate and demodulate optical signals directly.Finally,novel GPD-based three-dimension(3D)integrated optical receiver chips are fabricated and studied.A novel complementary metal-oxide-semiconductor(CMOS)post-backend process is developed for integrating GPDs onto the surface of silicon integrated circuit(IC)chips.A prototype 3D integrated optical receiver is successfully demonstrated for the first time.In addition,this is a broadband optical receiver benefited from the broadband light absorption features of graphene.Therefore,this GPD-based optical receiver can provide service to both short-and long-distance optical communication systems.This study is a perfect exhibition of the concept of 3D optoelectronic integration and will pave the way to integrate graphene optoelectronic devices with silicon ICs for a 3D optoelectronic integrated circuit(OEIC)chips.Novel buried-gate GFETs and GPDs,GFET-based frequency multipliers,GPD-based photoelectric mixers and optical receiver chips are demonstrated successively in this thesis.This work innovates in the fabrication technologies,devices and chips based on graphene and would lay a comprehensive foundation for the development and application of graphene RF devices and optoelectronic integrated chips.