Photodetectors Based On Graphene/Silicon Schottky Diode

Graphene is an attractive candidate for the application in the optoelectronic devices, due to its extraordinary optical and electrical properties, which leads to the strong research interest on it.In this thesis, In this thesis, graphene/silicon photodetector was fabricated using semiconductor manufacturing processes. Anti-parallel Schottky junction metal-semiconductor-metal structure photodetector was proposed and investigated. The main results are shown below:(1) First with the study of the mechanism that forming graphene/silicon Schottky junction, we fabricated a graphene/Si UV photodetector. The i-v characterization was used to study the rectification of the junction. The parameters of the diode was extracted from the i-v curve using thermionic theory:the ideality factor was 1.203, the barrier height was ～0.86 eV, the serial resistance was ～11 kΩ. From the analysis of the electric response of the Schottky diode under UV light, the mechanism of the photocurrent is:The incident photons were absorbed in the thin layer under the silicon surface and electron-hole pairs were generated under the UV light, these photon generated carriers were separated by the built-in electric field, forming the photocurrent. The optical response was measured at 0.17 A/W under the incident light with wavelength of 405 nm and power density of 0.1 mW/cm2.(2)In addition to the single graphene/silicon Schottky junction, we fabricated an MSM structure device which was anti-parallel graphene/silicon Schottky junction. We applied the following processes to reduce the dark current:1. Ailicon surface passivation which can suppress the leakage current between graphene and silicon; 2. adjust the shape of the silicon window will make the graphene/silicon Schottky junction with a larger junction area; 3. design a new fluorinated graphene-graphene planar heterojunction for MSM devices. Under illumination of UV light at wavelength of 405 nm and bias of 2 V, the photoresponsivity of the graphene MSM device is 0.68 A/W, while that of the fluorinated graphene MSM was 1.1 A[W, which was 62% larger than the former value.