Oriented Carbon Pair Defects Stabilized by Hydrogen in as-Grown GaAs Epitaxial Layers

We have studied the IR absorption of heavily carbon doped GaAs grown by metalorganic molecular beam epitaxy. A striking observation is that the hydrogen-stretching vibration of a Crelated complex at 2688 cm−1 is strongly polarized along just one of the <110> directions in the (001) growth plane. This polarized C-H vibration is assigned to a defect complex that is aligned at the growth surface and then maintains its alignment as it is incorporated into the growing crystal. In a series of experiments, we have studied the annealing of the 2688 cm−1 band and its alignment and suggest that the defect complex consists of a CAs-CAs pair stabilized by hydrogen.