Bandgap Energy of InGaAsP Quaternary Alloy

Abstract

The bandgap energy of InGaAsP quaternary alloy lattice-matched to InP has been precisely determined by electroreflectance (ER) measurements. The ER spectra show the typical low-field ER lineshape over the whole alloy composition range, and this has enabled us to determine the precise bandgap energy of the InGaAsP alloy easily. It was found that the bandgap energy E g of the In 1- x Ga x As y P 1- y alloy lattice-matched to InP is written as E g =1.35-0.738· y +0.138· y 2 at room temperature as a function of the As composition y . We have also measured the photoluminescence spectra of the InGaAsP samples, and found that the peak energy of the photoluminescence spectrum, which is frequently used as a measure of the bandgap energy, is slightly different from the precise bandgap energy determined by ER measurements.