ELECTRON-DENSITY EFFECTS IN THE MODULATION SPECTROSCOPY OF STRAINED AND LATTICE-MATCHED INGAAS INALAS/INP HIGH-ELECTRON-MOBILITY TRANSISTORSTRUCTURES/

The effects of the channel electron density on the interband optical t ransitions of strained (x = 0.6 and 0.65) and lattice-matched (x=0.53) InxGa1-xAs/In0.52Al0.48As/InP high-electron-mobility transistor struc tures have been investigated by phototransmittance at room temperature . Analysis of the ground and first excited transitions for low and hig h densities, respectively, enabled a separate estimation of the electr on densities occupying each one of the first two subbands. It was foun d necessary to include the modulation of the phase-space filling in th e analysis of the spectra, especially for the samples with a high elec tron density, in which case this modulation mechanism becomes dominant . (C) 1996 American Institute of Physics.