CRITICAL THICKNESS ANISOTROPY IN HIGHLY CARBON-DOPED P-TYPE (100)GAAS LAYERS GROWN BY METALORGANIC MOLECULAR-BEAM EPITAXY

The formation of misfit dislocations at the (100)GaAs substrate interfaces of thick highly carbon-doped p-type GaAs layers grown by metalorganic molecular beam epitaxy, was investigated using x-ray diffraction and transmission electron microscopy. The misfit dislocation lines were observed to be all aligned along one of the <011> directions on the substrate and were identified as being 'beta' type. Enhanced migration of beta-dislocations in p-type GaAs coupled with heterogeneous dislocation loop formation at clusters of partially dissociated (CH3)3Ga molecules is proposed as a probable cause of the anisotropy.