Abstract
In 2004,A.K Geim and K.S. Novoselov successfully isolated a single atomic carbon layer from HOPG using mechanical exfoliation methods. Since then, graphene has attracted enormous interest due to its unique properties. Amongst the physical properties of graphene, its high transmittance and conductive properties have shown great potential for photovoltaic applications. Within optoelectronics, the first choice for graphene applications lies within solar cells. Graphene / silicon Schottky junction solar cells, when compared with conventional ITO Schottky junction solar cell reap serious benefits from graphene technology; this in terms not only of device fabrication but also of materials, since graphene can be largely inexpensive to manufacture. In 2009, an IBM team used graphene for ultrafast optical sensors. Graphene’s high transmittance means light absorption cannot be readily achieved; as such the photo-response of graphene is not good as a CMOS sensor. This work focuses on improving photoresponsivity for graphene photodetectors. In addition to the inherent problem of graphene, obtaining graphene necessarily needs a transfer process, the transfer process lead to graphene being effectively combined with the CMOS process. This thesis uses two methods of obtaining graphene: Graphene from transfer process and graphene directly grown on silicon substrate by ECR-CVD. We fabricate two kinds of graphene-Schoktty junction photodetector. We analyze their junction characteristic and their photoelectric effect. The responsivity of pristine transfer graphene device is 301mA/W, doped transfer graphene device is 302 mA/W and ECR graphene device is 90mA/W.