Surfactant effects of dopants on ordering in GaInP

The use of surfactants for control of specific aspects of the VPE growth pr ocess is beginning to be studied for both the elemental and III/V semicondu ctors. The objective is to change the characteristics of the material grown epitaxially by the addition of a surfactant during growth. Most reported s urfactant effects for semiconductors relate to some detail of the morpholog y 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 arrang ement of the atoms in an alloy with a fixed composition, the change in orde r parameter induced by the surfactant translates into a marked change in th e 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 f ound to decrease or eliminate ordering; however? the mechanisms are quite d ifferent. The donor Te apparently affects the adatom attachment kinetics at steps on the (001) surface, a surfactant effect. On the other hand the don or Si was found to decrease the degree of order by an entirely different me chanism, 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 ts occur by the same mechanism. The isoelectroni c impurity Sb is found to act as a surfactant and to decrease the order par ameter by changing the surface reconstruction. eliminating the [<(1)over ba r 10>]-P dimers that provide the thermodynamic driving force for formation of the CuPt structure during growth.