MBE growth of GaSb on Ge-based templates grown on Si for mid-infrared photonics

We study the molecular beam epitaxy of GaSb layers on Ge-based templates grown on Si substrates by low-energy plasma-enhanced chemical vapor deposition. First, we study the growth mechanism to obtain a GaSb surface free of emerging antiphase boundaries on Ge substrates, and then we transfer this mechanism to Ge-based templates. Our investigations reveal that this mechanism is hindered by the crosshatch pattern formed during the Ge-based template growth. We demonstrate that using low-miscut (1°) Si substrates or chemical-mechanical polishing mitigates the effects of the crosshatch pattern, enabling the growth of GaSb layers free of emerging antiphase boundaries. These results represent a further step towards the monolithic integration of III-V on mid-infrared photonic platforms.