Comment on the compositional dependence of bandgap in AlGaAs and band-edge discontinuities in AlGaAs-GaAs heterostructures

Abstract

A range of values exists in the literature for compositional dependence of bandgap in Al_xGa_1-xAs below the direct-indirect alloy composition and the way this is apportioned between the conduction and valence band edges. The authors 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.