Photoluminescence spectra of n-doped double quantum wells in a parallel magnetic field

We show that the photoluminescence (PL) line shapes from tunnel-split groun d sublevels of n-doped thin double quantum wells (DQW's) are sensitively mo dulated by an in-plane magnetic field B-parallel to at low temperatures (T) . The modulation is caused by the B-parallel to-induced distortion of the e lectronic structure. The latter arises from the relative shift of the energ y-dispersion parabolas of the two quantum wells (QW's) in (k) over right ar row space, both in the conduction and valence bands, and formation of an an ticrossing gap in the conduction band. Using a self-consistent density-func tional theory, the PL spectra and the band-gap narrowing are calculated as a function of B-parallel to , T, and the homogeneous linewidths. The PL spe ctra from symmetric and asymmetric DQW's are found to show strikingly diffe rent behavior. In symmetric DQW's with a high density of electrons, two PL peaks are obtained at B-parallel to=0, representing the interband transitio ns between the pair of the upper (i.e., antisymmetric) levels and that of t he lower (i.e., symmetric) levels of the ground doublets. As B-parallel to increases, the upper PL peak develops an N-type kink, namely a maximum foll owed by a minimum, and merges with the lower peak, which rises monotonicall y as a function of B-parallel to due to the diamagnetic energy. When the el ectron density is low, however, only a single PL peak, arising from the tra nsitions between the lower levels, is obtained. In asymmetric DQW's, the PL spectra show mainly one dominant peak at all B-parallel to's In this case, the holes are localized in one of the QW's at low T and recombine only wit h the electrons in the same QW. At high electron densities, the upper PL pe ak shows an N-type kink like in symmetric DQW's. However, the lower peak is absent at low B-parallel to's because it arises from the inter-QW transiti ons. Reasonable agreement is obtained with recent data from GaAs/Al0.3Ga0.7 As DQW's. [S0163-1829(99)00411-7].