Characterization and modeling of the infrared properties of GaP and GaAs

Abstract

The experimental characterization of multiphonon absorption in polycrystalline GaP and GaAs asa function of temperature and frequency is presented. Because GaP and GaAs have moderate bandgaps,free carrier absorption is examined at high temperature as well. The longwave transparency and excellentthermal and mechanical properties of GaP make it a candidate for future high-stress environmentapplications. In this paper, a broadband FTJR transmissometer is used with a frequency range from 500 to5000 cm' for GaP and 400 to 5000 cm1 for GaAs. Spectral measurements were performed from 10 to 800K for GaP and 10 to 295 K for GaAs. In addition, high temperature laser transmittance measurementsusing HeNe lasers (632.8 nm and 3.39 tm) and a CO2 (10.6 rim) laser were conducted up to 1 100 K.Using this experimental data set, an updated multiphonon and free carrier absorption model is developedthat represents the experimental data over all temperatures and frequencies.Keywords: Multiphonon absorption, GaAs, GaP, and multiphonon and free-carrier absorption modeling