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Seminar 10/9/2013 - James Kolodzey, University of Delaware: Electronic and Optical Properties of GeSn Alloys and Junctions

Abstract: The mid-infrared region, covering wavelengths from about 2 to 5 micrometers, is becoming increasingly active because of new developments in materials as well as emerging applications.  With its good atmospheric transmission, the mid-IR is important for communications and remote sensing.  Many biochemicals have signatures in this wavelength region, which is also important for medical diagnostics. The technology of Group IV semiconductors has been moving down the periodic table to heavier elements, and the addition of tin to silicon and germanium is currently under investigation by several research groups.  For instance, the use of GeSn stressors in CMOS circuit technology is being investigated for higher performance transistors that use Ge-based active channels.  There is experimental and theoretical evidence that the energy bandgap of GeSn becomes direct in k-space for sufficient Sn content, above about 6 atomic percent, for the possibility of efficient optical devices.  In this talk, we report on the growth of GeSn using the non-equilibrium growth method of molecular beam epitaxy (MBE), which is challenging because Sn is not easily miscible in Ge.  Materials analysis shows that GeSn epitaxial layers can be grown with at least 14 % Sn, and they are single crystal with most of the Sn being substitutional in the Ge lattice.  GeSn can be doped and fabricated into p-n junctions with good rectifying I-V characteristics, and good photodetection in the mid-IR.  The junction devices can emit mid-IR light, which increases in intensity for Sn contents above about 6 %, which support evidence for the bandgap becoming direct at this composition.  This talk will present experimental results and discuss how GeSn is becoming an important material for fundamental studies and for practical applications in the mid-IR wavelength region.

All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Location: Bowen Hall Auditorium

Date/Time: 10/13/13 at 12:00 pm - 10/13/13 at 1:00 pm

Category: PRISM/PCCM Seminar Series

Department: PRISM