Electron confinement in planar-doped heterostructures AlxGa1−xAs:δSi/GaAs

Photoluminescence (PL) of the modulated doped heterostructures Al0.33Ga0.67As:δSi/AlxGa1−xAs:δSi/Al0.33Ga0.67As/GaAs is investigated for different compositions of x. A two-dimensional electron gas (2DEG) is formed at the heterointerface Al0.33Ga0.67As/GaAs due to the electron affinity difference between the two materials. The δ-doping is used to enhance the performance of quantum electronic and photoionic devices. Among these aspects, the presence of the DX centres in Al0.33Ga0.67As barrier can control the electron population in GaAs channel sub-bands. Low-temperature PL measurements show that the DX centre effects are reduced when the δ-doping plane is placed in a thin Al0.24Ga0.76As quantum well (QW) embedded in the Al0.33Ga0.67As barrier, and exhibit a PL band F associated to the radiative transitions of the 2DEG. The high-energy side of the band F is extended and reflects the form of √ shape of the channel conduction band. Combination of PL measurements of the band F with the results of a self-consistent Poisson–Schrödinger model has demonstrated that the Fermi energy is located at 110 meV above the Γ conduction band minimum of the channel. The PL study of these structures also reveals the presence of a large anti-stokes PL (ASPL) band at low temperature, situated at 100 meV above the bandgap of Al0.33Ga0.67As. The nonlinear ASPL intensity dependence on power excitation suggests a process of two-step two-photon absorption as origin of this PL.