6 research outputs found
Magnetic Field Induced Charged Exciton Studies in a GaAs/Al(0.3)Ga(0.7)As Single Heterojunction
The magnetophotoluminescence (MPL) behavior of a GaAs/Al(0.3)Ga(0.7)As single
heterojunction has been investigated to 60T. We observed negatively charged
singlet and triplet exciton states that are formed at high magnetic fields
beyond the nu=1 quantum Hall state. The variation of the charged exciton
binding energies are in good agreement with theoretical predictions. The MPL
transition intensities for these states showed intensity variations (maxima and
minima) at the nu=1/3 and 1/5 fractional quantum Hall (FQH) state as a
consequence of a large reduction of electron-hole screening at these filling
factors.Comment: submitted to Phys. Rev. Let
Negatively Charged Excitons and Photoluminescence in Asymmetric Quantum Well
We study photoluminescence (PL) of charged excitons () in narrow
asymmetric quantum wells in high magnetic fields B. The binding of all
states strongly depends on the separation of electron and hole layers.
The most sensitive is the ``bright'' singlet, whose binding energy decreases
quickly with increasing even at relatively small B. As a result, the
value of B at which the singlet--triplet crossing occurs in the spectrum
also depends on and decreases from 35 T in a symmetric 10 nm GaAs well
to 16 T for nm. Since the critical values of at which
different states unbind are surprisingly small compared to the well
width, the observation of strongly bound states in an experimental PL
spectrum implies virtually no layer displacement in the sample. This casts
doubt on the interpretation of PL spectra of heterojunctions in terms of
recombination