(color online) (a) The change in the channel resistance at 20 K as a function of δ-layer thickness. Panels (b) and (c) respectively show the relaxation of normalized resistance for different δ doping at 20 K and 300 K after switching off the illumination from a halogen lamp. The recovery dynamics follow a stretched exponential behavior, which is represented as solid lines in (b). The inset of (b) shows the relative change in the resistance at 300 K upon irradiating the samples with 325 nm and 441 nm lines of a He–Cd laser. A comparison of the photoresponse as a function of temperature for different samples is made in the inset of (c). The 0.5 monolayer LaMnO₃ shows a three-fold increase in the photoresponse by comparison with the δ = 0 sample.^[86]