Described herein are techniques for forming an epitaxial III-V layer on a substrate. In a pre-clean chamber, a native oxygen layer may be replaced with a passivation layer bytreating the substrate with a hydrogen plasma (or products of a plasma decomposition). In a deposition chamber, the temperature of the substrate may beelevated to a temperature less than 700°C. While the substrate temperature is elevated, a group V precursor may beflowed into the deposition chamber in order to transform the hydrogen terminated (Si-H) surface of the passivation layer into an Arsenic terminated (Si-As) surface. After the substrate has been cooled, a group III precursor and the group V precursor may beflowed in order to form a nucleation layer. Finally, at an elevated temperature, the group III precursor and group V precursor may beflowed in order to form a bulk III-V layer.