Ge Photodetectors

About

Technology Germanium (Ge) nanostructure material can be used in optoelectronic devices and solar cells such as high-efficiency, quantum dot (QD) photodetectors, silicon (Si) and Ge heteronanowire (hetero-NW) solar cells, and electrically pumped Si/Ge/Si-NW optical sources.  All use Ge/Si or Ge/oxide barriers to confine carriers and enhance photoconductive gain in detectors, optical absorption and spectral coverage in solar cells, and electrically pumped luminescence.  Approaches and target materials are compatible with the dominant silicon technology, enhancing quantum efficiency and spectral sensitivity, which are expanding to include alternative active materials like Ge and on-chip integration of optical sources and detectors.  Ge has some inherent limitations in optics, and accordingly there have been few reports of Ge-based optical sources.  However, Ge photodetectors exist and show promising performance.  The nanoscale size of the Ge active regions is beneficial to physical mechanisms, and the attractive physical properties of Ge QDs are excellent for optoelectronic devices and solar cells. The invention is comprised of novel fabrication methods to create two classes of Ge-based QD, silicon-compatible, materials and devices: 1) ultra-high efficiency photodetectors with high responsivity and a broad, flat spectral response in the visible to near-infrared wavelength range; 2) broad-spectrum tandem solar cells and electrically pumped optical emitters via Si/Ge hetero-NWs.  Fabrication can occur at lower temperatures for integration onto a silicon platform, and resultant devices can be operated at a relatively low reverse bias, compared to current approaches.  Light absorption by Ge QDs in a silicon substrate achieves a broader spectral response; therefore, high-efficiency photodetectors based on Ge QDs, easily integrated into a standard silicon complementary metal-oxide semiconductor process, is realized. This invention can be applied to the manufacture of solar cells, optical sources, and photodetectors or sensors, in the scientific, commercial and military market segments.  Industries include the computer/microelectronics, e.g., wafer bonding, and solar cell energy panel, among many others using photodetectors, optics and/or sensors.