Fig. 4

Spatial-resolved photocurrent images of D1 as a function of V _sd. a The optical image together with the electrical setup. b Spatial-resolved photocurrent images at V _bg = 0 V and V _sd = − 0.1, 0.01, 0, 0.01, and 0.1 V, respectively. c Spatial-resolved photocurrent images at V _bg = 5 V and V _sd varies from − 0.1 to 0.1 V. d Spatial-resolved photocurrent images at V _bg = 5 V and V _sd = 0.5 V. e I _PC profile at V _bg = 0 V and f I _PC profile at V _bg = 5 V taken along dashed line in Fig. 4a. The scale bars are 5 μm in all figures