Spectroscopic ellipsometry study of InP, GaInAs, and GaInAs/InP heterostructures

Abstract

The dielectric functions of high-purity InP and GaInAs layers grown by metal-organic vapor-phase epitaxy (MOVPE) have been measured in the 2.0–3.5-eV energy range using spectroscopic ellipsometry. Analysis of third derivatives computed from these data gives critical-point (E1 and E1+Δ1 transitions) energies, broadening parameters, and phases. The reference dielectric functions of InP and GaInAs are used to analyze GaInAs/InP and InP/GaInAs heterojunctions fabricated in a MOVPE reactor. The sharpest interface as measured by a multilayer modeling is 30 Å of GaInAsP at the interface of InP grown on GaInAs and 9 Å of InAs for GaInAs grown on InP. Dielectric functions of very thin GaInAs and InP layers (<100 Å) have been extracted from the data measured on heterostructures. It is demonstrated that these extracted dielectric functions are extremely sensitive to the interface quality and give further information about the quality of the MOVPE-grown thin layers of GaInAs and InP.