Structural and Optical Properties of AlGaN MQWs Grown by MOCVD Using One and Two TMG Sources

POSTER

Abstract

Multiple quantum wells (MQWs) are grown by metal-organic chemical vapor deposition (MOCVD) at a temperature of 1155 $^{\mathrm{o}}$C. The quantum well (QW) and the quantum barrier (QB) are designed to be Al$_{\mathrm{0.6}}$Ga$_{\mathrm{0.4}}$N and Al$_{\mathrm{0.75}}$Ga$_{\mathrm{0.25}}$N, respectively. One sample is grown by the traditional method with one Trimethylgallium (TMG) source. The other is grown with two TMG sources. In the one TMG configuration, the TMG flow rate needs to be changed for QW and QB. During this change, there is no Ga injecting onto the wafer surface, resulting Al-rich dark layers at the interfaces between QWs and QBs seen in the high-angle annular dark-field (HAADF) image. In two TMG configuration, QW and QB are grown by two TMG sources with different flow rates, allowing instantaneous switch between QW and QB. In the HAADF image, the interfaces exhibit no dark layer with better contrast between QW and QB. In the cathodoluminescence (CL) spectra, the two TMG sample shows a higher efficiency than the other by a factor of 7. In the one TMG sample, the Al atoms are mostly gathered at the interfaces, which leads to an ineffective quantum confinement as the width of the barriers is actually smaller than designed. The CL peak of the one TMG sample has shorter wavelength (257 nm) than the two TMG sample (263 nm), because the QW has an actual Ga content lower than 40{\%} and the Al-rich dark layers squeeze up the ground state in QW.

Authors

  • Shuo Wang

    Arizona State University

  • Yong Wei

    Arizona State University

  • Hongen Xie

    Arizona State University

  • Alec Fischer

    Arizona State University

  • Fernando Ponce

    Arizona State University

  • Scott D. Bergesen

    Santa Fe Institute, Arizona State University, Department of Physics and Center for Biological Physics, Arizona State University, Brigham Young University Department of Physics and Astronomy, Brigham Young University, Utah Valley University, Dixie State College, Advisor, Student, Massachusetts Institute of Technology, Thomas Jefferson National Accelerator Laboratory, Colorado College, United States Air Force Academy, Georgia Institute of Technology, Utah State University, Brigham Young University - Idaho, Utah State University- Logan, National Institute of Standards and Technology, Humboldt State University, UC Santa Cruz, Institut de Chimie des Substances Naturelles, Arizona State Univ, University of Colorado at Colorado Springs, National Jewish Health, Department of Physics, The University of Texas at Austin, Department of Physics, New Mexico State University, U. S. Air Force Academy, Brigham Young Univ - Provo, University of New South Wales, University of Texas, University of Warwick, University of Louisiana, Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA., Center for Materials Genomics, Department of Mechanical Engineering and Materials Science and Department of Physics, Duke University, Durham, North Ca, Duke University, Durham, North Carolina., Brigham Young University -- Provo, Utah, General Atomics -- San Diego, California, Department of Mathematics, University of British Columbia, Department of Physics, Arizona State University, UC Riverside, UMASS, STScI, NOAO, UT Austin, Texas A&M, Arizona State Univeristy, New Mexico State Univ, Los Alamos National Laboratory, Colorado State Univ, Department of Physics, Oregon State University, Colorado School of Mines, University of Alaska, Fairbanks, The Peac Institute of Multiscale Modeling, UNSW Canberra

  • Brendan Gunning

    Georgia Institute of Technology

  • Alan Doolittle

    Georgia Institute of Technology