High-Speed Carbon Nanotube Photodetectors for 2 mu m Communications

In the era of big data, the growing demand for data transmission capacity requires the communication band to expand from the traditional optical communication windows (similar to 1.3-1.6 mu m) to the 2 mu m band (1.8-2.1 mu m). However, the largest bandwidth (similar to 30 GHz) of the current high-speed photodetectors for the 2 mu m window is considerably less than the developed 1.55 mu m band photodetectors based on III-V materials or germanium (>100 GHz). Here, we demonstrate a high-performance carbon nanotube (CNT) photodetector that can operate in both the 2 and 1.55 mu m wavelength bands based on high-density CNT arrays on a quartz substrate. The CNT photodetector exhibits a high responsivity of 0.62 A/W and a large 3 dB bandwidth of 40 GHz (setup-limited) at 2 mu m. The bandwidth is larger than that of existing photodetectors working in this wavelength range. Moreover, the CNT photodetector operating at 1.55 mu m exhibits a setup-limited 3 dB bandwidth over 67 GHz at zero bias. Our work indicates that CNT photodetectors with high performance and low cost have great potential for future highspeed optical communication at both the 2 and 1.55 mu m bands.