Band Gap of 'Completely Disordered' Ga0.52In0.48P

The phenomenon of ordering in Ga_0.52In_0.48P is well known to reduce the optical band gap; the amount of band gap reduction is often used to measure the degree of ordering. For such measurements to be meaningful, the band gap of the random (]]completely disordered") binary alloy must be known. Values of this fundamental material parameter appearing in the literature vary by up to 40 meV, while the largest band gap reduction reported to date is only about 120 meV, i.e., within a factor of 3 of the uncertainty in one endpoint. We report here a low temperature band gap of 2.010±0.007 eV for material lattice matched to GaAs as deduced from a broad spectrum of samples believed for different reasons to contain minimal ordering. The corresponding value at 295 K is 1.910±0.008 eV.