High-sensitivity, fast-response broadband graphene photodetector on LiNbO₃

Abstract

Graphene has a zero-band gap structure with pho-todetection from visible to terahertz frequencies. Graphene also has high carrier mobility, making it suitable for optoelectronic applications. Lithium niobate is a polar crystal with a high pyroelectric coefficient. The laser absorbed by lithium niobate is converted into heat, and the change in temperature causes spontaneous polarization of the lithium niobate. The lithium niobate pyroelectric polarization induces the surface free electric charge to enter the graphene, and changes the Fermi level of the graphene, thereby improving the photoelectric performance of the device. In this work, the photodetector shows a responsivity of ~ 2.12×10 ⁶ A/W at 22pw incident power, high detectivity of 6.29 ×10 ¹⁴ Jones and wide detection rang from visible to near infrared. Particularly, the high rise/decay speed of 20ms/30ms is achieved. This work suggests that the lithium niobate has great potential for high-performance photodetectors.