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 exitonic 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 (E(M)). Hence, by adding the exciton binding energy to E(M), the value of the energy gap (E(G)) at each temperature has been deduced from the spectra. This way an accurate determination of the temperature dependence of E(G) in GaAs is obtained; values for the parameters of the semiempirical relations describing E(G)(T) are found and compared with the literature.