OBSERVATION OF OSCILLATORY LINEWIDTH BEHAVIOR IN THE MAGNETOLUMINESCENCE OF A MODULATION-DOPED INXGA1-XAS QUANTUM-WELL

Low-temperature magnetophotoluminescence measurements on a modulation- doped pseudomorphic Al0.25Ga0.75As/In0.20Ga0.80As/GaAs layer in fields up to 8 T are reported. The zero-field spectrum shows two features, a broad luminescence peak at 1.305 eV with an exponential decay towards higher energy, arising from transitions between electrons in the fill ed lowest electron subband and photogenerated holes, and a sharp peak at 1.346 eV due to an excitonic transition involving the second electr on subband. As the magnetic field is increased, Landau-level-related s tructure appears within the broad feature, and this line shape has bee n analyzed in terms of a series of Gaussian peaks superimposed on a sl owly varying linear background. The broadening factor, T, of the Landa u levels oscillates with increasing magnetic field, with minimum value s corresponding to integer numbers of filled levels; such behavior is opposite to that observed previously in Si and InAs, where the effects have been explained by self-consistent screening. We propose that the oscillations are due to field-dependent variations in scattering rate . The background also shows oscillatory behavior, and this may account in part for the wide variations between background density-of-states values reported in earlier measurements on two-dimensional systems.