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0907296_Paiella

Direct- Bandgap Light Emission from Tensile Strained Germanium Nanomembranes Roberto Paiella , Trustees of Boston University, DMR 0907296.

odette-sheppard
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0907296_Paiella

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  1. Direct-Bandgap Light Emission from Tensile Strained Germanium NanomembranesRoberto Paiella, Trustees of Boston University, DMR 0907296 The development of efficient light emitting diodes and lasers based on Si, Ge, and related group-IV semiconductors has long been a major research goal, as it would enable the monolithic integration of electronic and photonic devices on an unprecedented scale. This goal has so far been hindered by the indirect nature of the energy bandgap of these materials, which results in exceedingly low light-emission efficiency. A possible solution is the use of tensile strain in Ge, which has been theoretically predicted to modify the electronic properties leading to direct-bandgap behavior. Here we have shown that large tensile strain can be introduced in Ge via mechanical deformation of free-standing nanomembranes, leading to strongly enhanced light-emission efficiency. Top: optical micrograph of a Genanomembrane (NM). Bottom: measured photoluminescence spectra of a similar NM under various amounts of pressure introducing tensile strain. A strong increase in light-emission efficiency with increasing strain is clearly observed.

  2. Silicon-Based Nanomembranes Fabrication and Charge Transport MeasurementsRoberto Paiella, Trustees of Boston University, DMR 0907296 During the past year, the Lagally group at UW – Madison employed several undergraduate research assistants and hosted a SURE student working on activities related to this project. Lauren Brzozowski, now a sophomore, has been instrumental in helping students in the microelectronics fabrication facility, and with atomic force microscopy. The SURE student, Abbie Hill, conducted van derPauw measurements on nanomembranes and worked to resolve some of the complications surrounding electrical measurements of extremely small structures. Her REU experience culminated in an hour-long poster presentation where she was able to display her achievements to faculty, staff, and students. Sophomore electrical engineering student Lauren Brzozowski adjusting atomic force microscope for nanomembrane surface measurement.

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