Black Phosphorus Schottky Diodes: Channel Length Scaling and Application as Photodetectors

Black phosphorus (BP) Schottky diodes with asymmetric metal contacts are demonstrated using gold and aluminum electrodes. The devices exhibit rectifying characteristics with current rectification ratio up to 1.5 × 10³. The effect of channel length on the electrical characteristics of the BP Schottky diodes is also studied and the results reveal that the device loses its rectifying behavior (rectification ratio = 1.37) at ultrashort channel length of around 30 nm. The transition from rectifying to nonrectifying characteristics at extremely small channel length is attributed to the electric-field-induced barrier thinning, which results in significantly increased tunneling current under reverse bias. Using the BP Schottky diodes with relatively long channel length (≈1 μm), photodetectors with fast response time of less than 2 ms are demonstrated. This work demonstrates the potential of using BP-based diode devices for optoelectronic applications.