Optical method of estimation of degree of atomic ordering within quaternary semiconductor alloys

It is well known that within metal-organic vapor-phase epitaxy grown semiconductor ternary alloys atomically ordered regions are spontaneously formed during the epitaxial growth. This ordering leads to bandgap reduction and to valence bands splitting, and therefore to anisotropy of the photoluminescence emission polarization. The same phenomenon occurs within quaternary semiconductor alloys. While the ordering in ternary alloys is widely studied, for quaternaries there have been only a few detailed experimental studies of it, probably because of the absence of appropriate methods of its detection. Here, we propose an optical method to reveal atomic ordering within quaternary alloys by measuring the photoluminescence (PL) emission polarization. The measured and calculated angular dependencies of the polarized PL emission intensity from (100) surface for two semiconductor alloys: Ga0.51In0.49P and (Al0.3Ga0.7)(0.5)In0.5P are compared in order to estimate the degree of atomic ordering within these alloys. The method shows that the quaternary (Al0.3Ga0.7)(0.5)In0.5P alloy is a highly ordered structure with the value of the atomic ordering degree close to 0.5. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737574]