Anomalous relaxation in combined low and high temperature growth of InGaAs/GaAs epilayers

Transmission electron microscopy study of low temperature grown In0.2Ga0.8As/GaAs heterostructures showed an unexpected Lomer dislocation network with a low density, located in the upper part of the epilayer. This result is very promising for their higher misfit relieving component and lower mobility compared to 60° type dislocations. Epitaxial growth of high quality III-V semiconductor thin layers needs to overcome the reticular misfit accommodation challenge to avoid the formation of crystalline defects, that is, threading dislocations which can pass through the active layers of these heterostructures reducing carrier mobility and constituting non-radiative recombination centers. The formation of a Lomer misfit dislocation network inside a buffer layer that relaxes more effectively the reticular mismatch is an excellent tool for buffer layer design. Several mechanisms have been proposed to explain Lomer dislocation formation in semiconductor heterostructures. For the climb process, a dislocation must move from its glide plane to a parallel one through the diffusion of vacancies in the material.Peer reviewe