Room-temperature optical absorption in the InAs/GaAs quantum-dot superlattice under an electric field

Electroluminescence and absorption spectra of a ten-layer InAs/GaAs quantum dot (QD) superlattice built in a two-section laser with sections of equal length is experimentally studied at room temperature. The thickness of the GaAs spacer layer between InAs QD layers, determined by transmission electron microscopy, is ∼6 nm. In contrast to tunnel-coupled QDs, QD superlattices amplify the optical polarization intensity and waveguide absorption of the TM mode in comparison with the TE mode. It is found that variations in the multimodal periodic spectrum of differential absorption of the QD superlattice structure are strongly linearly dependent on the applied electric field. Differential absorption spectra exhibit the Wannier-Stark effect in the InAs/GaAs QD superlattice, in which, in the presence of an external electric field, coupling of wave functions of miniband electron states is suppressed and a series of discrete levels called the Wannier-Stark ladder states are formed.