ALIGNED DEFECT COMPLEX CONTAINING CARBON AND HYDROGEN IN AS-GROWN GAAS EPITAXIAL LAYERS

A hydrogen-stretching vibration at 2688 cm(-1), previously observed in heavily-carbon-doped GaAs grown by metal-organic molecular-beam epitaxy and assigned to a defect complex that contains carbon and hydrogen, has been studied by infrared-absorption spectroscopy. The absorption at 2688 cm(-1) has been found to be preferentially polarized along a particular [110] axis in the (001) growth plane. We propose that this band is due to a complex that is aligned at the growth surface and then maintains its alignment as the crystal is grown. The annealing of the 2688-cm(-1) band and its alignment have been examined. We also find that the 2688-cm(-1) complex can be formed by annealing heavily-carbon-doped GaAs between 500 and 650 degrees C in the presence of hydrogen. These results provide insight into the interactions of carbon and hydrogen in heavily-carbon-doped GaAs and lead us to tentatively assign the 2688-cm(-1) band to a (C-A2)(2)H complex. We suggest that the annealing of this center and of its alignment is due to the dissociation and reassociation of C-As pairs that are controlled by the presence of hydrogen.