A semiconductor structure, a method, and an apparatus for in-situ sulfur vapor passivation of an interface surface of an indium gallium arsenide layer of the semiconductor structure. A method includes elemental sulfur-vapor passivation of an interface surface of an indium gallium arsenide layer disposed on a substrate. A dielectric layer can be deposited on the sulfur-vapor passivated interface surface. An annealing process can be performed after the deposition of the dielectric layer. The annealing process anneals the indium gallium arsenide layer including the sulfur-vapor passivated interface surface and the dielectric layer disposed on the sulfur-vapor passivated interface surface. The sulfur-vapor passivation, the deposition of the dielectric layer, and the anneal, can be performed in-situ in a vacuum chamber without breaking a vacuum of the vacuum chamber following a III-V material growth process in the vacuum chamber to form the indium gallium arsenide layer.