Abstract
Photodetectors are ubiquitous, found in everyday products such as TV remotes, disc players and digital cameras as well as specialized devices for fiber optic communications and astronomical observations. Similarly, graphene has seen a quick emergence in a range of prototypic devices due to its attractive electronic, optical and mechanical properties.1 Using graphene in photodetection utilizes its high carrier mobility and zero bandgap that—among other advantages—show promise for wide-spectrum, high-speed, low-cost and flexible photosensors. Graphene-based photodetectors have typically relied on Schottky barriers formed near the metal–graphene contacts, where a built-in potential drives the separation and transport of photogenerated electron–hole pairs. However, symmetric metal–graphene–metal devices generate an equal positive and negative flow with a net zero photocurrent (Figure 1a). Using metals with asymmetric band structures breaks this equilibrium2 (Figure 1b) at the cost of additional fabrication steps and is limited by the maximum difference in barrier heights. Recently, Liu and co-workers3 from Peking University presented a step forward by creating a single p–n junction in graphene itself.
Highlights
In this study, adjacent regions of intrinsic (p-type) and nitrogen-doped (n-type) graphene form a junction with a potential offset at the center of the device
The synthesis is built upon their previous work on ‘mosaic graphene’:4 by modulating the doping concentrations during a chemical vapor deposition process, they form coherent regions of distinctly nitrogen-rich and -deficient graphene
While low absorption is great for transparent conductors, in photodetectors it leads to low photoresponsivity
Summary
Adjacent regions of intrinsic (p-type) and nitrogen-doped (n-type) graphene form a junction with a potential offset at the center of the device. Photodetectors are ubiquitous, found in everyday products such as TV remotes, disc players and digital cameras as well as specialized devices for fiber optic communications and astronomical observations. Graphene has seen a quick emergence in a range of prototypic devices due to its attractive electronic, optical and mechanical properties.[1] Using graphene in photodetection utilizes its high carrier mobility and zero bandgap that—among other advantages—show promise for wide-spectrum, high-speed, low-cost and flexible photosensors.
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