SAIP2025

An anomaly in a formula to calculate the refractive index of Al_xGa_1-xAs

Not scheduled

20m

Solomon Mahlangu House (University of the Witwatersrand, Johannesburg)

Poster Presentation Track A - Physics of Condensed Matter and Materials Poster Session

Speaker

Japie Engelbrecht (Nelson Mandela University)

Description

A formula to calculate the refractive index n of Al_xGa_1-xAs was proposed by Adachi in 1985. This formula takes into account the variation of the band gap E_g of Al_xGa_1-xAs as function of the Al mole fraction x. Consequently there are two equations for the calculation of the band gap, viz. for x less than 0.45 and x from 0.45 to less than 1. The refractive index is used to calculate the thickness of epilayers of Al_xGa_1-xAs grown by metallorganic vapour phase deposition, whereafter infrared reflectance spectra were obtained from respective samples with various mole fractions. The mole fraction x can also be obtained from the reflectance spectra. When calculating the required refractive indexes, the applicable equation for the band gap should be used depending on whether x is less than 0.45 or whether x is greater than 0.45 but less than 1. An anomaly was observed when the epilayer thickness was calculated using the formulation of Adaci, and results will be presented to demonstrate the anomaly.