Figure 2. Electric-doping dependent photoluminescence spectra at room temperature in vacuum.
(a) Colour contour plot of normalized PL spectra excited by a cw laser (2.331 eV) under various back-gate bias. Dashed black arrows contour PL peaks of free exciton and trion states. Even at zero gate bias the trion X− exists due to defects or substrate interactions. (b) Illustration of the PL profile at Vg = −20 V (dashed line labelled in the top panel) as a superposition of two Lorentzian shape lines in red. (c) Electric gate dependence of excitons′ and trions′ energies (upper panel) and the corresponding integrated intensities (bottom panel).