SiGe Nanomembrane Characterization Roberto Paiella, Trustees of Boston University, DMR 0907296

1. SiGe Quantum-Well Nanomembranes for THz Quantum-Cascade Laser ApplicationsRoberto Paiella, Trustees of Boston University, DMR 0907296 SiGe quantum wells (QWs) are promising candidates for the development of THz quantum cascade lasers capable of closing the existing “THz gap” of optoelectronics, with the additional advantage of intrinsic CMOS compatibility. However, the demonstration of these devices has so far been hindered by the large lattice mismatch between Si and Ge, which leads to the formation of extensive strain-induced defects in SiGe QWs grown on Si substrates. To overcome this issue, we have developed a new fabrication approach where SiGe QWs are grown on a previously released SiGe nano-membrane, whose lattice constant matches that of the epitaxial material in its elastically relaxed state. As shown in the figure, x-ray-diffraction and intersubband-absorption-spectroscopy data indicate that high-quality samples can indeed be formed with this approach. Fabrication procedure (top), x-ray diffraction data (bottom left) and intersubband absorption spectrum (bottom right) of a SiGe QW nanomembrane sample. P. Sookchoo, F. F. Sudradjat, A. M. Kiefer, R. Paiella, and M. G. Lagally, manuscript in preparation

2. SiGe Nanomembrane CharacterizationRoberto Paiella, Trustees of Boston University, DMR 0907296 During the past year, the Lagally group at UW – Madison has employed five undergraduate research assistants, four male and one female. Max Burton, pictured using the atomic force microscope, is the newest one. He is a junior in Materials Science and Engineering, and has been primarily working on activities related to this project. The two components of the project are growing strained structures for potential SiGe quantum cascade lasers and Ge nanomembrane strain engineering for direct-band-gap light emission. One of the graduate students working on this project, Jose Sanchez Perez, is a Fellow in the UW – Madison Graduate Engineering Research Scholars (GERS) program (http://gers.engr.wisc.edu/), which aims to attract graduate students from underrepresented groups into engineering disciplines. An additional GERS scholar in the Lagally group performs research on projects unrelated to this grant. Max Burton, an undergraduate laboratory aide, is pictured while making surface roughness measurements with the atomic force microscope.