Optical and magneto-optical absorption of negatively charged excitons in three- and two-dimensional semiconductors

The line shape of the optical and magneto-optical absorption of negatively charged excitons in three- and two-dimensional (2D) semiconductors has been studied. The absorption coefficients have been determined using envelope wave functions obtained by variational means. At zero field, the charged exciton lines are disposed at the low-energy side of the threshold frequency with a rapidly decreasing long tail. In the two-dimensional case, the maximum corresponds to the threshold frequency, while in the 3D case, this maximum is shifted to lower transition energies. The magnetic field gives rise to a Landau quantization of the spectra, which reduces to a series of sharp lines in the two dimensional case. [S0163-1829(98)02639-3].