Interface grading in InGaAsP liquid phase epitaxial heterostructures

Auger depth profiles on InGaAs-InP and InGaAs-InGaAsP heterojunctions grown by liquid phase epitaxial (LPE) techniques have been measured. For InGaAs-InP and InGaAsP-InGaAs-InGaAsP heterostructures where the lattice mismatch Δa/a between the grown layers is less than ±0.03%, the chemical transition width of the InGaAs-InP and InGaAs-IGaAsP interfaces (the last-grown layer is listed first) is less than 90 Å, the depth resolution capability of the Auger microprobe in these measurements. In contrast, the chemical transition width of the lattice-matched InGaAsP-InGaAs interface is significantly larger than this. This increased transition width results from significant dissolution of the InGaAs epitaxial layer by the InGaAsP growth solution which is controlled by the diffusion of As from the interfacial region. These results suggest that it may be impossible to avoid grading at LPE InP-InGaAs interface.