Fabrication of penetrating pores in epitaxial Ge-on-Si through preferential etching along threading dislocations

• Published in: Electrochimica acta 2024-07, Vol.493, p.144416, Article 144416
• Main Authors: Zhu, Ying, Zhang, Yiwen, Li, Bowen, Xia, Guangrui (Maggie), Wen, Rui-Tao
• Format: Article
• Language: English
• Subjects: Ge-on-Si; Porous germanium; Preferential etching; Threading dislocations
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2024.144416

•Preferential etching at TD sites takes place in the porosification process of Ge-on-Si and is independent of the doping type and concentration.•For the morphology of penetrating pores, the porous Ge was in a dense columnar shape when the holes were supplied adequately. When the hole concentration is limited, dendritic pore shape was obtained, for example, in n-type Ge-on-Si with a doping concentration of 5E18 cm−3.•The penetrating pores at the TDs follow the path of the threading dislocation line and form a conical shape of the etched region. Since the TDs thread from the Ge/Si interface to the Ge surface, the etching along dislocations would ultimately penetrate the entire epitaxial Ge layer.•The origins of the preferential etching at TDs have been discussed to be lattice distortion in structure and negative charged in dislocation cores. Epitaxial Ge-on-Si possesses a high density of threading dislocations (TDs) due to the lattice mismatch and difference in thermal expansion coefficient. By employing the lattice distortion at the TDs, we demonstrate that penetrating pores along TDs can be formed in both p- and n-type heteroepitaxial Ge layers through a preferential etching. It has been found that the preferential etching at TD sites takes place in the porosification process of Ge-on-Si samples and is independent of the doping type and concentration. The penetrating pores follow the path of the TD lines and can penetrate the entire Ge layer of 1.3 μm to further porosificate the Si substrate. The effects of anodic current density and total etching duration have been thoroughly investigated on forming penetrating pores at TD sites. The dissolution mechanism in the porosification process has been revealed by dissolution valence calculation and recorded potential curves. Our findings shed light on Ge perforation in both p- and n-type Ge-on-Si and show great potential in Si-based integrated photonics and microelectronics.