Effects of Br and Cl on organometallic vapor phase epitaxial growth and ordering in GaInP

Abstract

CuPt ordering in GaInP has significant effects on the electrical and optical properties. In fact, band gap reductions as large as 160 meV are potentially useful for devices. Thus, control of ordering is important. This has led to the investigation of surfactants that affect the surface processes during growth with little incorporation into the solid. A potentially interesting class of surfactant elements are those from group VII, that are known not to be incorporated during growth, but to change the dynamics of surface processes. This article describes the results of the addition of Cl and Br during the organometallic vapor phase epitaxial growth of GaInP. The addition of Br in small concentrations is observed to systematically decrease the amount of CuPt ordering observed directly via transmission electron diffraction and photoluminescence measurements. A ratio of Br/III of 0.042 is found to virtually eliminate ordering. The reduction in order parameter is not found to correspond to a decrease in the 405 nm peak measured during in situ surface photoabsorption measurements. This indicates that a change in surface reconstruction is not responsible for the decrease in order parameter. However, both Cl and Br are found to significantly roughen the surface morphology. Atomic force microscopy shows that facets are formed that increase in height and angle to the (001) growth surface as the surfactant concentration increases. This is postulated to be the origin of the reduction in order parameter, since previous studies have indicated that an intentional misorientation of the substrate in either the A or B direction leads to a decrease in order parameter.