Removal of Ge Islands in al-induced layer-exchanged Ge thin films on glass substrates by selective etching technique

Al-induced layer-exchanged Ge (ALILE-Ge) combined with epitaxy is a promising way to fabricate advanced electronic optical devices on foreign substrates as well as Si large-scale integrated circuits. The presence of Ge islands on the surface of the ALILE-Ge seed layer was a problem because the islands deteriorated the crystal quality of the epitaxial layer. This paper gives a solution to this problem: the Ge islands were selectively etched by H2O2 treatment. The ALILE-Ge seed layer was protected by using the oxidized Al membrane, prepared between Ge and Al, as an etching mask. By initially preparing the thick Ge layer and then removing the excess Ge islands, we improved the coverage of the ALILE-Ge seed layer on the substrate. The resulting ALILE-Ge provided a high (111) orientation fraction (96%) and large grains (> 100 μm). This Ge layer appears promising for use in seed layers for epitaxial Ge, group III-V compound semiconductors, and other advanced materials.