High-precision determination of the temperature dependence of the fundamental energy gap in gallium arsenide

The photoluminescence (PL) spectra of GaAs have been measured as a function of temperature between 2 and 280 K. Measurements have been performed on a high-quality nominally undoped sample grown by molecular-beam epitaxy. At the lower temperatures the recombination of free excitons in the n=1 and 2 states is observed. Increasing the temperature, the interband recombination appears and eventually dominates the PL spectra. The spectra have been successfully fitted by a spectral-line-shape theory that considers both excitonic and band-to-band transitions. The fits demonstrate that even at the highest temperatures a well-defined narrow peak due to the n=1 exciton is observable: its energy corresponds to the energy of the maximum of the PL spectra (${\mathit{E}}_{\mathit{M}}$). Hence, by adding the exciton binding energy to ${\mathit{E}}_{\mathit{M}}$, the value of the energy gap (${\mathit{E}}_{\mathit{G}}$) at each temperature has been deduced from the spectra. This way an accurate determination of the temperature dependence of ${\mathit{E}}_{\mathit{G}}$ in GaAs is obtained; values for the parameters of the semiempirical relations describing ${\mathit{E}}_{\mathit{G}}$(T) are found and compared with the literature.