Effect of strain and ordering on the band-gap energy of InGaP

The band-gap energy (Eg) of strained and ordered InGaP ternary compound was studied using precise room-temperature ellipsometric measurements and low temperature photoluminescence (PL) with the aim to compare the degree of order evaluated from these measurements. All samples under study were prepared by MOVPE epitaxial growth at a temperature of 640 °C and a reactor pressure of 20 mbar. Our results have shown that the band gap energy of InGaP follows closely the compositional dependence proposed in the literature. The degree of order value obtained from low temperature PL is about three times higher as it follows from a precise evaluation using the Weiʹs and Zungerʹs prediction and room temperature ellipsometry experimental data.