Electron-Hole Plasma Diffusion in Direct-Gap Semiconductors?

Spatially resolved gain and luminescence spectra of the electron-hole plasma have been measured in GaAs and Ga 0.60 Al 0.40 As at liquid-He temperature. Diffusion lengths smaller than 4 μm, i.e. the experimental spatial resolution have been measured at electron-hole pair densities as high as ten times the "liquid density". Further, it is shown that the density profiles deduced from luminescence measurements do not reflect the real carrier distribution. Diffusion lengths and drift velocities reported for other direct-gap semiconductors are also discussed.