The growth of strain engineered germanium tin alloys for mid-infrared detectors by molecular beam epitaxy

Date
2017
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Interest in near and mid-infrared optoelectronic devices for sensing, security, medical imaging, and telecommunications has led to an immense effort to create new materials capable of filling these needs. As the applications for these infrared devices have become more ubiquitous, so too does the desire for cheaper and more efficient materials to meet the demand. As the industry pushes more towards complete device integration, there is also a heavy push specifically towards developing materials compatible with standard CMOS processing. To that end, the alloying of Tin with Germanium and Silicon has been shown to fit these requirements. ☐ During the course of this research on germanium-tin semiconductors, novel methods were developed for growing and fabricating electrical and optical devices with unusually high tin compositions, using silicon-compatible technology. The characteristics and limitations of the devices were measured and analyzed to understand their fundamental properties and to determine how well their performance compared to expectations from current theory. With increasing tin content, the optical devices exhibited a useful direct energy bandgap, which is unique compared to other Group-IV materials, and with operation extended from the near-infrared into the important mid-infrared wavelength regime, even into the long-wave infrared region. The performance of electronic devices, however, was less encouraging, and exhibited low carrier mobilities and high reverse leakage currents. These electrical properties were found partly due to the intrinsic narrow bandgap energy of germanium-tin, but also to the presence of background impurities and dopants, which it may be possible to reduce by using high purity materials and procedures that are compatible with the required low temperature epitaxy.
Description
Keywords
Applied sciences, GeSn, Germanium tin, Infrared detectors, MBE, Molecular beam epitaxy
Citation