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Chang Y.C.,National Tsing Hua University | Chang Y.C.,Catholic University of Leuven | Merckling C.,Interuniversity Microelectronics Center vzw | Penaud J.,Riber | And 10 more authors.
Device Research Conference - Conference Digest, DRC | Year: 2010

The quest for technologies beyond the IS nm node complementary metal-ox ide-semiconductor (CMOS) devices has now called for research on alternative channel materials such as Ge and III-V compound semiconductors with inherently higher carrier mobility than those of Si. Intensive effort has been made on GaAs nMOS devices owing to GaAs's superior electron mobility and its lattice parameter close to that of Ge. Dielectric/GaAs (100) interfaces, in general, have very high interfacial trap density (Dit) at the mid-gap energy,1-3 resulting in serious Fermi-level pinning issues, and thus preventing the proper inversion response required for the inversion-channel GaAs MOS devices. To solve this problem, a number of approaches for passivating GaAs have been reported in the past decades,4-10 with one report showing good drain current in an inversion-channel GaAs MOSFET.10 Evaluation of Dit was usually obtained using capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics measured at room temperatures. However, due to the larger energy band-gap of GaAs as compared to that of Si, interfacial traps near the mid-gap of the dielectric/GaAs interfaces may be too slow to respond to the usual C-V and G-V characterization frequencies at room temperatures and only a small region of the whole GaAs band-gap away from the mid-gap can be measured.2,3,11 In this work, this inadequacy is remedied by performing additional C-V and G-V measurements at a high temperature of 150°C to probe Dit spectrums near the critical mid-gap region. Furthermore, the influence on the Dit around the mid-gap region of the dielectric/GaAs interfaces by the GaAs surface reconstructions and systematic annealing conditions has been studied. © 2010 IEEE.

Paetzold U.W.,Forschungszentrum Juelich GmbH | Paetzold U.W.,Interuniversity Microelectronics Center Vzw | Lehnen S.,Forschungszentrum Juelich GmbH | Bittkau K.,Forschungszentrum Juelich GmbH | And 2 more authors.
IEEE Journal of Photovoltaics | Year: 2015

Nanophotonic light management concepts are essential building blocks of advanced thin-film solar cells. These concepts make use of light coupling to waveguide modes that are supported by the photoactive absorber material of the solar cell. In a recent study, we presented a new method based on scanning near-field optical microscopy that enables the direct nanoscale investigation of light coupling to an individual waveguide mode in a nanophotonic thin-film silicon solar cell. Making use of this method, we investigate in this contribution the polarization dependence of the light coupling to a waveguide mode. Based on this polarization dependence, we can attribute the investigated waveguide mode to a transverse electric mode. Moreover, we identify the grating vector, which is responsible for the light coupling to the investigated waveguide mode in the nanopatterned thin-film silicon solar cell. © 2011-2012 IEEE.

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