Relationship between the conduction band discontinuities and band gap differences.

We have measured the magnitude of the conduction band discontinuities at heterojunctions for several compositions of InGaAsP grown lattice-matched on InP. We find that the conduction band discontinuity (deltaE(c)) is related to the difference in band gaps (deltaE (g)) between the InGaAsP and InP layers via: deltaE(c) = 0. 394(deltaE(g)). Thus, 40% of the band gap difference lies in the conduction band of this material system, in contrast to GaAs/GaAlAs heterojunctions, where 85% of the band gap difference lies in the conduction band.