Effect of growth parameters on step structure and ordering in GaInP

Abstract

Ga 0.52In 0.48P layers have been grown by organometallic vapor phase epitaxy using various values of substrate temperature, tertiarybutylphosphine (TBP) flow rate, and growth rate on singular (0 0 1) GaAs substrates. The surface structure, measured using high resolution atomic force microscopy, consists of small islands surrounded by either monolayer or bilayer steps. An increase in the TBP flow rate at 670°C leads to a change in the step structure from mainly monolayer steps at low flow rates to predominantly bilayer steps at high flow rates. The increased TBP flow rate also results in an increase in the degree of order in the epitaxial layers. Changing the growth rate over a limited range for a constant TBP flow rate gives no change in either the step structure or the degree of order of the epitaxial layer. This preliminary data suggests that, contrary to previous reports, a change in growth rate in the range 0.25–0.5 μm/h has no inherent effect on the ordering process. The step structure also changes from predominately monolayer to bilayer as the growth temperature increases from 520 to 700°C. A possible kinetic model is proposed for this process. Again, the most highly ordered layers are those with the highest fraction of bilayer steps on the surface during growth. Together, these data appear to suggest the importance of bilayer steps in the ordering process, although it is difficult to separate the effects of the step structure from those associated with the changes in surface reconstruction caused by the variations in temperature and P partial pressure.