Room-temperature photoreflectance (PR) and photoluminescence (PL) spectra in heavily n-doped
G&U were compared. It was found that for highly degenerate semiconductors the critical energy
measured by the PR equals to the peak energy of the PL spectrum. When Fermi level lies below the
conriIlction-bartd minimum, the PR spectra revealed the band-gap energy as well as the energy E,,,
at which the electron concentration per unit energy in the donor band becomes maximum, and this
mnsimum was observed to merge in the conduction-band at about 3X lOI cm -3 electron
concentration.