Fig. 1. (a) Schematic illustration of the BP photodetector. (b) SEM image of the BP photodetector with Au electrodes. (c) AFM image of BP nanoflakes showing a thickness of ∼20  nm. (d) Representative Raman spectrum of BP.

Fig. 2. (Color online) (a) Power-dependent photocurrent as a function of source-drain voltage (VSD) at 635 nm. (b) Energy diagram illustrating the photocurrent generation with and without bias. (c) Gate-tunable source-drain current (ISD) with and without light illumination. Laser wavelength: 635 nm, VSD=0.1  V. (d) Time-dependent photocurrent at 635 nm with a light power of 400 nW. VSD=0.1  V. (e) Rise time (10% to 90%) and fall time (90% to 10%) of BP photodetector device at 635 nm. (f) Photocurrent and responsivity as functions of the incident light power at 635 nm.

Fig. 3. (Color online) (a) Power-dependent source-drain current (ISD) as a function of the source-drain bias (VSD) at 980 nm. Inset is a zoom in of the ISD–VSD curve. (b) Time-dependent photocurrent under different incident light powers at 980 nm. VSD=0.1  V. (c) Photocurrent and responsivity as functions of the incident light power at 980 nm. (d) Time-dependent photocurrent with varying incident light powers at 1550 nm. VSD=1  V. (e) Rise time (10% to 90%) and fall time (90% to 10%) of our device at 1550 nm. (f) Photocurrent and responsivity as functions of the incident light power at 1550 nm.