Figure 8.

Metal/2D material structures. (a) Metal–graphene–metal (MGM) photodetectors with asymmetric metal contacts. (b) The dotted line denotes the Fermi level. $\Delta {\varphi }_{Pd}$ and $\Delta {\varphi }_{Ti}$ represent the difference between the Dirac point energy and the Fermi level in palladium- and titanium-doped graphenes, respectively. (c) Relative photoresponse versus light intensity modulation frequency. The -3dB bandwidth of this MGM photodetector is 16 GHz. Inset: receiver eye-diagram obtained using this MGM photodetector, showing a completely open eye. (d) Photodetectors with asymmetric contact geometries. (e) Photodetectors with different degrees of asymmetries. (f) Weyl semimetal scanning photocurrent response. (a–c) reproduced with permission from [5]. Copyright Nature Publishing Group, 2010. (d,e) reproduced with permission from [90]. Copyright Wiley 2019. (f) Reproduced with permission from [91]. Copyright Nature Publishing Group, 2019.