Fourier transform infrared (FTIR) absorption spectra and photoluminescence (PL) spectra for PbSe0.78Te0.22and Pb0.95Sn0.05Se0.80Te0.20layers grown by liquid phase epitaxy on (100) BaF2substrates are reported. FTIR absorption edges varied from 213 to 275 meV (between 4 and 300 K) for the ternary alloy and from 118 to 200 meV (between 10 and 300 K) for the quaternary alloy. PL energies were 174 meV at 5 keV for the ternary alloy and 100 meV at 7.1 K for the quaternary alloy. The differences between the low temperature FTIR absorption edge energies and the PL energies are attributed to the Burstein–Moss effect. ©1995 American Institute of Physics.