High-k gate stacks on low bandgap tensile strained Ge and GeSn alloys for field-effect transistors

© 2014 American Chemical Society. Este artículo está firmado por 14 autores. Authors thank to Valery Afanasiev, Catholic University of Leuven, for useful suggestions and discussions regarding Dit extraction. One of the authors, M.A Pampillon, thanks for funding by the FPI program (BES-2011-043798 and EEBB-I-13-07086) of the Spanish “Ministerio de Economía y Competitividad”. This work was partially supported by the German Federal Ministry of Education and Research under the project “Ultralow Power”. ; We present the epitaxial growth of Ge and Ge_(0.94)Sn_(0.06) 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 5nm Al_(2)O_(3), 5nm HfO_(2) or 1nm Al_(2)O_(3)/4nm HfO_(2), on strained Ge and strained Ge_(0.94)Sn_(0.06). 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. ; Depto. de Estructura de la Materia, Física Térmica y Electrónica ; Fac. de Ciencias Físicas ; TRUE ; Spanish “Ministerio de Economía y Competitividad” program FPI ; German Federal Ministry of Education and Research ; pub