STUDIES OF 2-SUBBAND OCCUPIED ELECTRON-GAS IN MODULATION-DOPED IN0.52AL0.48AS IN0.53GA0.47AS SINGLE-QUANTUM-WELL BY FAR-INFRARED MODULATED PHOTOLUMINESCENCE/

We report an investigation of electronic and optical properties of two -subband occupied electron gas confined in Al0.48In0.52As/Ga0.47In0.53 As quantum well by far-infrared (FIR) modulated photoluminescence (PL) measurements. We show that, in addition to the characterization of th e effective mass and Fermi energy, this technique is a useful tool for the understanding of the luminescence processes. Well-resolved Landau -level splittings were observed in the FIR modulated PL spectrum at a fixed magnetic field. It is found that the PL spectrum involves the tr ansitions between localized holes and electrons at all occupied k stat es. For the FIR modulated spectrum monitored at the peak position as a function of magnetic field, a strong double cyclotron-resonance signa l was observed. The double structure of cyclotron resonance is attribu ted to the cyclotron transitions in the first and second subbands. The obtained effective masses are found to be considerably heavier than t he bulk value by 22% and 46% for the first and second subband, respect ively. The heavier effective mass of the second subband is opposite to the behavior measured in the triangular quantum well. We point out th at, in order to explain the enhanced masses, both the effects of band nonparabolicity and wavefunction penetration into the barrier material have to be taken into account. (C) 1998 American Institute of Physics .