High‑k Gate Stacks on Low Bandgap Tensile Strained Ge and GeSn Alloys for Field-Effect Transistors

• Published in: ACS applied materials & interfaces Vol. 7; no. 1; pp. 62 - 67
• Main Authors: Wirths, Stephan, Stange, Daniela, Pampillón, Maria-Angela, Tiedemann, Andreas T, Mussler, Gregor, Fox, Alfred, Breuer, Uwe, Baert, Bruno, San Andrés, Enrique, Nguyen, Ngoc D, Hartmann, Jean-Michel, Ikonic, Zoran, Mantl, Siegfried, Buca, Dan
• Format: Journal Article Web Resource
• Language: English
• Published: United States American Chemical Society 14.01.2015
• Subjects: field-effect transistor; GeSn; high-k dielectrics; low bandgap alloys; Physical, chemical, mathematical & earth Sciences; Physics; Physique; Physique, chimie, mathématiques & sciences de la terre; strained Ge; GeSn; high-k dielectrics; field effect transistor; strained Ge; low bandgap alloys
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/am5075248

We present the epitaxial growth of Ge and Ge0.94Sn0.06 layers with 1.4% and 0.4% tensile strain, respectively, by reduced pressure chemical vapor deposition on relaxed GeSn buffers and the formation of high-k/metal gate stacks thereon. Annealing experiments reveal that process temperatures are limited to 350 °C to avoid Sn diffusion. Particular emphasis is placed on the electrical characterization of various high-k dielectrics, as 5 nm Al2O3, 5 nm HfO2, or 1 nmAl2O3/4 nm HfO2, on strained Ge and strained Ge0.94Sn0.06. Experimental capacitance–voltage characteristics are presented and the effect of the small bandgap, like strong response of minority carriers at applied field, are discussed via simulations.