Determination of Heterointerface Band Alignments in nBn Photodetectors Using Off-Axis Electron Holography

ORAL

Abstract

The zero valence-band offset between the barrier and absorber of a nBn photodetector is challenging to achieve practically, which could lead to different electrical characteristics. Long-wave (Sample A) and mid-wave (Sample B) infrared nBn photodetectors with absorbers consisting of InAs/InAsSb SLs and barriers consisting of InAs/AlGaSb(As) SLs, were grown using MBE. Distinctively different electrical characteristics suggested the possibility of different types of band alignments between the barrier and absorber for these two devices, which was attributed to the difference in Ga composition in the barrier layer. Examination of the barrier layers using off-axis electron holography showed the presence of positive charge with an estimated density of 1.8\texttimes 10\textasciicircum 17/cm\textasciicircum 3 in Sample B as a result of a type-II band alignment, whereas negligible charge was detected in Sample A, consistent with a type-I band alignment. This staggered type-II alignment of Sample B caused the significant increase in its dark current when strong bias is applied, because electrons from the valence band of the barrier layer can tunnel to the conduction band of the absorber layer.

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Authors

  • Xiao-Meng Shen

    Arizona State University

  • Zhao-Yu He

    Arizona State University

  • Shi Liu

    Arizona State University

  • Yong-Hang Zhang

    Arizona State University

  • Dave Smith

    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