Measurements of the transition energies of GaAsSb quantum well samples with different barrier configurations reveal that the conduction band offset of the coherently strained ${\mathrm{GaAs}}_{1-y}{\mathrm{Sb}}_y∕\mathrm{GaAs}$ heterojunction grown on GaAs has a zero crossing at a Sb mole fraction of $y=0.43\pm 0.07$. A type-I band alignment is formed for lower Sb mole fractions and a type-II band alignment is formed for higher Sb mole fractions. This occurs as a consequence of a considerable amount (58%) of the $-1.58\mathrm{eV}$ bandgap bowing being distributed to the conduction band. As a suitable active material for 1.3 μm emission, pseudomorphic ${\mathrm{GaAs}}_{0.643}{\mathrm{Sb}}_{0.357}$ grown on GaAs is determined to have a weak, $23\pm 23\mathrm{meV}$, type-I conduction band offset and a bandgap energy of $928\pm 4\mathrm{meV}$.

• Received 25 August 2004

DOI:https://doi.org/10.1103/PhysRevB.70.195339