Electron density effects in the modulation spectroscopy of strained and lattice-matched InGaAs/InAlAs/InP high-electron-mobility transistor structures

The effects of the channel electron density on the interband optical transitions of strained (x=0.6 and 0.65) and lattice-matched (x=0.53) InxGa1–xAs/In0.52Al0.48As/InP high-electron-mobility transistor structures have been investigated by phototransmittance at room temperature. Analysis of the ground and first excited transitions for low and high densities, respectively, enabled a separate estimation of the electron densities occupying each one of the first two subbands. It was found necessary to include the modulation of the phase-space filling in the analysis of the spectra, especially for the samples with a high electron density, in which case this modulation mechanism becomes dominant

Degenerate electron gas effects in the modulation spectroscopy of pseudomorphic Al0.32Ga0.68As/In0.15Ga 0.85As/GaAs high electron mobility transistor structures

The effects of a degenerate two-dimensional electron gas on the interband optical excitations, occurring in the active channel of Al0.32Ga 0.68As/In0.15Ga0.85As/GaAs high electron mobility transistor structures, were investigated by using phototransmittance spectroscopy. The ground state transition at room temperature exhibited a characteristic steplike line shape, which was considered to be an effect of the screening of excitons by the degenerate electron gas. A line shape fitting by using a first derivative of the absorption coefficient with respect to the electron sheet concentration ns, allowed an estimation of the latter quantity by phototransmittance. An observed temperature-sensitive excitonlike signal, associated with the second electron subband was attributed to the modulation of the many-body correlation-enhanced excitonic absorption, known as the Fermi-edge singularity

Degenerate electron gas effects in the modulation spectroscopy of pseudomorphic Al0.32Ga0.68As/In0.15Ga0.85As/GaAs high electron mobility transistor structures

The effects of a degenerate two-dimensional electron gas on the interband optical excitations, occurring in the active channel of Al0.32Ga0.68As/In0.15Ga0.85As/GaAs high electron mobility transistor structures, were investigated by using phototransmittance spectroscopy. The ground state transition at room temperature exhibited a characteristic steplike line shape, which was considered to be an effect of the screening of excitons by the degenerate electron gas. A line shape fitting by using a first derivative of the absorption coefficient with respect to the electron sheet concentration n(s), allowed an estimation of the latter quantity by phototransmittance. An observed temperature-sensitive excitonlike signal, associated with the second electron subband was attributed to the modulation of the many-body correlation-enhanced excitonic absorption, known as the Fermi-edge singularity