Relationship between the conduction-band discontinuities and band-gap differences of InGaAsP/InP heterojunctions

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 (ΔEc) is related to the difference in band gaps (ΔEg) between the InGaAsP and InP layers via ΔEc =0.39(ΔEg). Thus, 40% of the band-gap difference lies in the conduction band of this material system. The measurements were made on a series of composition of InGaAsP spanning the alloy range from In0.53Ga0.47As (with energy gap Eg =0.75 eV) to InP (Eg =1.35 eV) using capacitance-voltage techniques. Depletion deep into the semiconductor layers was facilitated by the formation of organic-on-inorganic semiconductor contact barriers on the InGaAsP surface.