Room‐temperature photoreflectance (PR) and photoluminescence (PL) spectra in heavilyn‐doped GaAs 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 conduction‐band minimum, the PR spectra revealed the band‐gap energy as well as the energyEmaxat which the electron concentration per unit energy in the donor band becomes maximum, and this maximum was observed to merge in the conduction‐band at about 3×1017cm−3electron concentration. ©1995 American Institute of Physics.