Isoelectronic surfactant-induced surface step structure and correlation with ordering in GaInP

Abstract

This paper explores the effects of surfactants isoelectronic with P on the step structure and ordering in GaInP grown by organometallic vapor phase epitaxy. Three elements, Bi, Sb, and As, were studied individually by adding them during epitaxial growth using the precursors trimethylbismuth, triethylantimony, and triethylarsenic. Atomic force microscopy was used to investigate the influence of the surfactants on the epilayer step structure. Bi produces a remarkable change in the step structure. A Bi concentration in the vapor of (Bi/III) v=1.65×10 −2 increases the [1 1 0] step velocity by nearly an order of magnitude. The addition of Bi leads to the complete elimination of three-dimensional islands and a significant reduction in surface roughness for layers grown on singular (0 0 1) GaAs substrates. These observations suggest that the surfactant Bi alters the attachment kinetics of group III adatoms at descending and ascending steps. When a comparable amount of surfactant Sb is added [(Sb/III) v=1.2×10 −2] the [1 1 0] step velocity increases only slightly. However, this amount of Sb also produces smoother surfaces. Higher amounts of the surfactant Sb [(Sb/III) v=6.4×10 −2] produce surface undulations with a period of ∼120 nm. These undulations are related to formation of a lateral compositional modulation. No step structure change occurs when a high partial pressure of As is added during growth [(As/III) v=3.3×10 −1]. Addition of each of the three isoelectronic elements has been observed to disorder GaInP layers that would otherwise be highly ordered.