Plasma enhanced atomic layer deposition of crystallized gallium phosphide on Si with tri-Ethylgallium and tri-tert-Butylphosphine

Abstract

25 ∼ 30 nm thick polycrystalline gallium phosphide (GaP) films with high P / Ga atomic ratios were deposited on Si (100) using a plasma enhanced atomic layer deposition (PE-ALD) process with triethyl gallium (TEG), tri-tertiary butyl phosphide (tri-TBP), and atomic hydrogen. The key is chemical functionalization of the Si (100) surface since the wet-cleaned Si surface is nearly inert to TEG and tri-TBP. In-situ Auger spectroscopy was employed to identify the most successful functionalization which employed a gas phase mixture of atomic hydrogen and tri-TBP consistent with formation of a surface phosphide layer on Si(100); this layer efficiently nucleated the PE-ALD of GaP. The crystallinity and surface roughness of GaP films were tuned by controlling the pulse length of atomic H plasma, showing the self-limiting ALD film growth with 2.7 Å/cycle. The optimal crystallized GaP thin film on 6°-miscut Si showed local epitaxy growth of homogeneous GaP epi-layers in transmission electron microscopy (TEM).