Surfactant effects of dopants on ordering in GaInP

The use of surfactants for control of specific aspects of the VPE growth process is beginning to be studied for both the elemental and III/V semiconductors. The objective is to change the characteristics of the material grown epitaxially by the addition of a surfactant during growth. Most reported surfactant effects for semiconductors relate to some detail of the morphology of the growing films. For ordered semiconductor alloys the effects can be much more dramatic, including major changes in the electrical and optical properties. Since the bandgap energy is dependent on the microscopic arrangement of the atoms in an alloy with a fixed composition, the change in order parameter induced by the surfactant translates into a marked change in the bandgap energy. This paper presents the results of a study of the effects of n-type (Te and Si), p-type (Zn), and isoelectronic (Sb) dopants on the ordering process in GaInP grown by OMVPE. All of the dopants studied were found to decrease or eliminate ordering; however, the mechanisms are quite different. The donor Te apparently affects the adatom attachment kinetics at steps on the (001) surface, a surfactant effect. On the other hand the donor Si was found to decrease the degree of order by an entirely different mechanism, attributed to an increase in the Ga and In diffusion coefficients in the bulk. It apparently does not involve the surface. Disordering due to the acceptor Zn was found to occur by the same mechanism. The isoelectronic impurity Sb is found to act as a surfactant and to decrease the order parameter by changing the surface reconstruction, eliminating the [1̄10]-P dimers that provide the thermodynamic driving force for formation of the CuPt structure during growth.