GOALI: BGaAs and BGaInAs Detectors Lattice-Matched to Silicon

University Of Texas At Austin, Austin TX

Investigators

Abstract

Nontechnical: Integrated circuits based on silicon have transformed modern life. They are the basis of microelectronics and digital computers. Silicon has also been used for optoelectronics devices that convert light into electricity, such as solar cells and photodetectors, or electricity into light, such as light-emitting diodes and lasers. However, silicon is sensitive only to visible light and a limited portion of the infrared spectrum. Also, the speed with which silicon-based devices can detect light is fundamentally limited. This project will study a new family of boron-containing materials that are sensitive to a broader range of infrared light as well as greatly increased speed of detection. One key advantage of these materials is that their crystal structure is compatible with silicon. This allows for them to be grown as high-quality crystals directly on silicon and take advantage of the sophisticated silicon manufacturing infrastructure. This project will demonstrate several types of photodetectors, as well as determine the fundamental physical properties necessary to gauge their ultimate potential. Applications include autonomous vehicles, communication systems, and biomedical instrumentation. The project will also provide unique mentoring and research experiences for graduate, undergraduate, and high school students. Outreach activities will include inspiring K - 12 students through classroom visits, as well as events like Science Thursdays and the Edison Lecture Series. Technical: Monolithic integration of direct bandgap, lattice-matched, semiconductor alloys with silicon remains a holy grail of photonics for both lasers and photodetectors. The resulting devices would enable tremendous advances in functionality for silicon-based photonic integrated circuits, with applications ranging from imaging systems and laser radar, to telecommunications, chemical sensing, etc. Current approaches towards monolithic integration of direct bandgap materials on silicon suffer from a variety of challenges, and there is no clear path to the lattice-matched materials needed to address important emerging applications in the near- and mid-infrared. A solution to this critical challenge is proposed: one focused on BGaInAs photodetectors on silicon that could span cutoff wavelengths from 1 to 5 microns. It is underpinned by the commercial availability of GaP/Si substrates, as well as the team's recent success demonstrating (1) record high boron contents up to ~22% into GaAs, nearly sufficient to lattice-match with silicon, (2) prototype pn and pin BGa(In)As photodetectors and light emitting diodes on GaAs, and (3) successful initial growths of coherent direct bandgap BGaAs on GaP and GaP/Si. While the focus will be on realizing direct bandgap lattice-matched photodetectors, it is important to note this approach will be applicable to emitters as well. This project will couple the expertise of the University of Texas at Austin with molecular beam epitaxial growth and device fabrication of epitaxial BGa(In)As photodetectors with the mid-infrared nBn detector expertise of Amethyst Research Inc. to: (1) realize high-performance pn- and pin-junction photodetectors on silicon, (2) illuminate and quantify the accessible bandgaps and band alignments on silicon and GaAs, and (3) use these properties to design and demonstrate silicon-based nBn detectors in the 3-5 micron range. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.