The relaxation of heavily C-doped GaAs which had been grown onto (001) GaAs substrates was investigated by using transmission electron microscopy and X-ray diffraction. It was found that a significant introduction of misfit dislocations occurred only above the Matthews-Blakeslee critical thickness. The onset of relaxation was delayed when the C concentration was increased. The resultant strain relaxation was highly anisotropic, with the introduction of As-cored misfit dislocations being entirely suppressed at the highest C levels; resulting in cracking of the epilayer. Locking of As-cored partial dislocations, and a reduction in the misfit dislocation velocity, were proposed as causes of the anisotropy and lack of relaxation.

S.P.Westwater, T.J.Bullough, T.B.Joyce, B.R.Davidson, L.Hart: Applied Physics Letters, 1997, 70[1], 60-2