A Study Of Graphene Photodetector Based On PPLN Substrate

Graphene is a material of great promise for various novel devices due to its unusually high electron mobility, atomic layer thickness and unique optic character. In recent years, It has attracts researcher’s attention in various fields, various novel characters of graphene in different devices had been reported. Photodetector is a significant device in optic communication, photograph, and other related field. Because of the unique electric and optic character, graphene had shown its potential in optoelectronic field. A well-known structure of graphene detector is the FET (Field Effect Transistor) structure. In FET structure graphene device, the band structure of graphene can be adjust by the different work function of metal electrode and graphene, which drive the separation of electron-hole pair. In this article, we investigate a graphene photodetector based on PPLN, the main contents are:1. we raise a new structure of graphene photodetector, which combine PPLN (Periodically Poled Lithium Niobate) and graphene, adjust the band structure of graphene. In the vicinity of niobate lithium domain interface, the graphene band structure has changed, and the Fermi surface also moved. When the electrons move through the domain interface from different direction, the device will present different resistance. With the variation of graphene band structure, the electron-hole pair which excited by incident photon can be separated. Through the electrode designed precisely, the electrons and holes can be collected by the source electrode and drain electrode. Compare with the FET structure graphene photo detector, the device based on PPLN will not occur a zero net current, which caused by the "back to back" metal graphene contact. And eventually achieve a better detection efficiency.2. Through transfer graphene to a PPLN substrate, lithography and electron beam evaporation, we can get the graphene photodetector based on PPLN. In the test of electrical transport properties, the device present different resistance when we take different bias voltage direction on source and drain. This result demonstrates that the PPLN can adjust the band structure of graphene.3. We find the PPLN can affect the optic properties of the photoresist. The variation of the photoresist produce a contrast under the microscopy, the contrast can achieve a non-destructive observation on the PPLN substrate. This phenomenon may inspire a new way for observing of ferroelectric domain.