Study of CuPt-type ordering and dopant effect of In(sub 0.5)Ga(sub 0.5)P/GaAs using spectroscopic ellipsometry

摘要

The CuPt-type ordering and dopant effects of In(0.5)Ga(0.5)P/GaAs epitaxial layers have been studied using spectroscopic ellipsometry and transmission electron microscopy. The degree of ordering was estimated by both transmission electron diffraction and direct band edge, E(sub 0). Conventional lineshape fitting of E(sub 1), E(sub 1)+(Delta)(sub 1), and E(sub 2) gaps using the second derivative of pseudo dielectric functions shows that the peak position and oscillator strength of the E(sub 1) gap are basically a function of CuPt-type ordering whereas their broadening and phase depend mainly on carrier concentration. The decrease of E(sub 1) gap is explained in terms of CuPt-type ordering. In contrast to the E(sub 1) gap, all the lineshape parameters of the E(sub 2) gap depend mainly on CuPt-type ordering. This difference is discussed in terms of apparent (open quotes)CuAu-type ordering(close quotes) or Y2 structure which was observed by transmission electron diffraction.