Abstract

The energy of the indirect X exciton in AlxGa1-xAs epitaxial layers (with 0.38 < x < 0.81) has been determined by photoluminescence measurements at a sample temperature of 12 K; from these data, the dependence on the Al concentration x of the energy of the GAMMA-X gap has been obtained: E(g)X(x) = 1.988 + 0.207x + 0.055x2 eV. This relation is characterized by a very small bowing. From our data we deduce also the coordinates of the GAMMA-X crossover point: x(c) = 0.385 +/- 0.016 and E(c) = 2076 +/- 4 meV at T = 0 K and x(c) = 0.396 +/- 0.016 and E(c) = 1997 +/- 4 meV at T = 300 K.

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