Terahertz photoluminescence in doped nanostructures with spatial separation of donors and acceptors

Terahertz (THz) luminescence in doped nanostructures with GaAs/AlGaAs quantum wells is studied under conditions of interband optical pumping. The study is carried out on compensated quantum wells with different doping profiles. In one structure, compensation is carried out directly in each quantum well by introducing donors and acceptors with the same concentration. In the other, donors and compensating acceptors are spatially separated, namely, donors are located in quantum wells, while acceptors are located in barriers. The spectra of THz photoluminescence are studied at various temperatures and levels of optical excitation. It is shown that the main contributions to the THz emission in both structures are due to the electron transitions from the first electron subband and excited donor states to the ground donor states. It is found that the spatial separation of donors and acceptors provides an approximately twofold increase in the integrated intensity of THz emission. This is directly related to the increase in the rate of dynamic depopulation of the ground donor levels due to the optical transitions from the ground donor states to the first heavy-hole subband, which is confirmed by photoluminescence studies in the near-infrared spectral range.