High performance Ge/graphene IR photodiode using chemical doping

Abstract

Currently, photodetector in NIR (Near Infra Red, wavelength : 750 ~ 3000nm) is used in wide area such as optical communication area, autonomous car, distance sensor, medical sensor device. However, in the case of the semiconductor used in the commercialized NIR photodetector, a complicated process and an expensive cost have become a problem. On the other hand, graphene photodetector has the advantages of being able to react in a wide wavelength range, transparent, flexible, and operating at a high speed, so graphene photodetector has been actively studied. However, despite these advantages, the graphene photodetector has a higher dark current in a light-free environment than a commercial semiconductor photodetector, and the photoresponsivity is very low (~ 100times). Then the graphene photodetector cannot completely replace semiconductor photodetector. In order to overcome these problems, studies on photodetector using junction of graphene and Germanium which is high responsivity in NIR have been carried out. This graphene/Ge hybrid photodetector operates using a photoresponse due to a Schottky barrier formed between Ge and graphene, but this also has a lower responsivity than commercial detectors. In this study, the experiment proceeded to increase the photoresponsivity by increasing or decreasing the Schottky barrier between Ge and graphene by adjusting the Fermi level of graphene through the chemical doping of graphene. After graphene chemical doping, device characteristics were compared.