Fig. 2: Controlling the diffusion behavior.

a–c Spatial mapping of the diffused IE PL emission at E_og = −0.023, 0, and 0.114 V/nm. The outer gate and the stripe gate areas are labeled V_og and V_sg, respectively. White dashed arrow indicates positive x direction. Red circle is the excitation position. Bright spots that naturally occur on the sample are reduced with the trapping potential. d Normalized PL along the x direction, averaged over the uniform y-cut trap region, as a function of E_og. The dotted lines correspond to the E_og line cuts in (e). The white dashed lines indicate the expected trap width of ∼ 500 nm. e Line cuts (scatter) and Gaussian fittings (lines) at E_og = −0.023, 0, and 0.114 V/nm showing narrowing (broadening) of the diffusion width when forming a trap (anti-trap). f Extracted diffusion width and relative peak intensity (PL_peak(E_og)/PL_peak(E_og = 0)) as a function of E_og. We observe the trap saturates near E_og ≈ 0.04 V/nm. Error bars come from the fitting of the spatial PL distribution. Note that “a.u.” is the abbreviation for “arbitrary units”.