http://dspace-roma3.caspur.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Thu, 23 May 2013 19:34:32 GMT 2013-05-23T19:34:32Z http://dspace-roma3.caspur.it/image/logo_roma3.jpg http://dspace-roma3.caspur.it:80 http://hdl.handle.net/2307/347 <Title>N-type SiGe heterostructures for THz intersubband transitions</Title> <Authors>De Seta, Monica; Capellini, Giovanni; Evangelisti, Florestano; Busby, Yan</Authors> <Issue Date>2009</Issue Date> <Pages>513-514</Pages> <Abstract>Research on band-gap engineering of Silicon-Germanium heterostructures for the realization of Quantum Cascade (QC) structures emitting in the Terahertz (THz) spectral region has recently attracted a vast interest. While several successful attempts have been reported using hole-based (p-type) intersubband transitions, very few results have been published on systems exploiting electrons (n-type). In this work we present the optical and structural characterization of n-type heterostructures made either of tensely-strained Si (sSi) quantum well (QW) confined between low Ge content Si1-xGex barriers [0.2<x<0.5] or of compressively-strained Ge (sGe) QW confined between high Ge content Si1-xGex barriers [0.8<x<0.9]. The structural and morphological characterizations of the samples have been made by atomic force microscopy (AFM), X-ray photoemission spectroscopy (XPS), transmission electron microscopy (TEM), and Raman spectroscopy. Intersubband transitions have been experimentally investigated by absorption spectroscopy and compared with the theoretical results of a tight-binding model, which provides the electronic band structure of the complete multi quantum well system throughout the whole Brillouin zone.</Abstract> Wed, 31 Dec 2008 23:00:00 GMT http://hdl.handle.net/2307/347 2008-12-31T23:00:00Z http://hdl.handle.net/2307/314 <Title>Conduction band intersubband transitions in Ge/SiGe quantum wells</Title> <Authors>De Seta, Monica; Capellini, Giovanni; Busby, Yan; Evangelisti, Florestano; Ortolani, Michele; Virgilio, Michele; Grosso, Giuseppe; Pizzi, Giovanni; Nucara, Alessandro; Lupi, Stefano</Authors> <Issue Date>2009-08</Issue Date> <Is part of>Applied Physics Letters</Is part of> <Volume>95</Volume> <Pages>051918-051918-3</Pages> <Abstract>In this letter we present the experimental evidence of intersubbandabsorption in the conduction band of compressively strained germaniumquantum wells bounded by Ge-rich SiGe barriers. The measured absorptionenergies are in the terahertz range and are interpreted by means oftight binding calculations which include self-consistent band-bendingand depolarization effects. From the comparison of experimental andnumerical results a conduction band offset along the L line of about120 meV has been estimated for the studied heterostructures.</Abstract> Fri, 31 Jul 2009 22:00:00 GMT http://hdl.handle.net/2307/314 2009-07-31T22:00:00Z