COMMENT ON THE COMPOSITIONAL DEPENDENCE OF BANDGAP IN ALGAAS AND BAND-EDGE DISCONTINUITIES IN ALGAAS-GAAS HETEROSTRUCTURES

A range of values exists in the literature for compositional dependence of bandgap in AlxGa1-xAs below the direct-indirect alloy composition and the way this is apportioned between the conduction and valence band edges. We compare results obtained from studies of compositionally graded quantum-well structures with consensus values and find that a self-consistent picture emerges only if a larger bandgap dependence than is still widely quoted in the literature is used. The preferred relation for bandgap dependence is DELTA-E(g)(x) = 1.427x + 0.041x2 (eV) with a conduction-to-valence band split ratio of about 60 : 40, yielding DELTA-E(c) = 0.88x and DELTA-E(v) = 0.55x.