Triplet transitions of ${\mathit{D}}^{\mathrm{-}}$ centers in quantum wells in high magnetic fields

The spin-singlet and spin-triplet optical transitions of negative donor centers ${\mathit{D}}^{\mathrm{-}}$ in GaAs/(Al,Ga)As quantum wells in high magnetic fields are considered both theoretically and experimentally. The measured and calculated transition energies are shown to be in very good agreement for the ${\mathit{D}}^{\mathrm{-}}$ singlet transition (1%). The two strong triplet transitions that are predicted by theory are not observed in the experiment. This is thought to be due to accidental energy coincidences with one-particle excitations such as the electron cyclotron resonance and the 1s→2${\mathit{p}}^{+}$ transition of neutral donors.