Nucleation and growth of GaSe on GaAs by Van der Waal epitaxy

Nucleation and growth of GaSe on GaAs(1 1 1)B substrate was studied to develop a better understanding of the Van der Waals epitaxy (VDWE) process. A complementary combination of RHEED, XPS, AFM and HREM were used. The initial GaAs(1 1 1)B surface reacts with incoming flux, forming a compound similar to GaSe at the surface. After one monolayer coverage, further growth of GaSe is on GaSe; the system changes from a heteroepitaxial to homoepitaxial system. Nucleation in the VDWE process is characterized by the formation of small oriented clusters with the weak Van der Waals bond dictating the orientation relationship. Further growth is found to be limited by surface kinetics, with a large diffusion barrier at the growing step edge. This barrier leads to islanding with the island shape dictated by the substrate temperature. A modified deposition procedure was developed to obtain uniform layer-by-layer growth of well-aligned flat GaSe domains without islanding.