False-color map of the 2 nd derivative of reflectivity as a function of the gate voltages (left axis) and the corresponding E z (right axis). The intensity of the strongest neutral A 1s exciton transition is intentionally saturated to reveal the behaviour of the weaker interlayer transitions. Note, that at negative electric fields, E z <−0.5 V/nm, the device is unintentionally doped, thus for simplicity, we focus on the analysis of the positive E z > 0 electric field data.
