Investigation and Characterization of Defects in Epitaxial Films for Ultraviolet Light Emitting Devices Using FUV Time-Resolved Photoluminescence, Time-Resolved Cathodoluminescence, and Spatio-Time-Resolved Cathodoluminescence Excited Using Femtosecond Laser Pulses

Abstract

Impacts of structural and point defects on the carrier (exciton) recombination dynamics in wide bandgap semiconductors such as AlN, high AlN mole fraction AlxGa1-xN alloys, and GaN were studied in this project. For this purpose, we quantified the radiative lifetimes (Tau/R) and nonradiative lifetimes (Tau/NR) for the near-band-edge (NBE) emission by measuring the luminescence lifetimes (Tau) and equivalent values of internal quantum efficiencies (eta/int) as a function of temperature by means of deep ultraviolet (DUV) time-resolved photoluminescence (TRPL) and time-resolved cathodoluminescence (TRCL) measurements using a frequency-quadrupled (4/omega) femtosecond Al2O3:Ti laser and pulsed electron beams generated using an in-house pulsed photoelectron-(PE) gun driven by the a frequency-tripled (3/omega) femtosecond laser, respectively. By comparing these lifetime data with the results of structural characterizations and positron annihilation spectroscopy (PAS) measurement, we correlated the lifetimes and cation vacancy concentrations. We also developed a spatio-time-resolved cathodoluminescence (STRCL) measurement system first equipped with a rear-excitation configuration pulsed PE-gun and later replaced by a front-excitation configuration one for probing local carrier dynamics in wide bandgap semiconductors. This technique enabled to measure spatially- and time-resolved luminescence signals even at DUV wavelengths. For demonstrating the improved PE-gun performances, spatially-resolved cathodoluminescence (SRCL) and local TRCL measurements were carried out on GaN, AlGaN, AlN, and hexagonal BN powders using the new STRCL system.

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Document Details

Document Type
Technical Report
Publication Date
May 22, 2013
Accession Number
ADA587678

Entities

People

  • Kouji Hazu
  • Shigefusa F. Chichibu

Organizations

  • Tohoku University

Tags

Communities of Interest

  • Advanced Electronics
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Advanced Materials
  • Compound Semiconductors
  • Crystal Lattices
  • Electronic Mail
  • Emission
  • Femtosecond Lasers
  • Mass Spectrometry
  • Measurement
  • Optical Properties
  • Optics
  • Point Defects
  • Quantum Efficiency
  • Semiconductors
  • Solid State Physics
  • Spectra
  • Spectroscopy
  • Wide Bandgap Semiconductors

Fields of Study

  • Materials science

Readers

  • Chemistry (specifically Chemical Fluorescence)
  • Optical Physics and Photonics.
  • Semiconductor Device Technology

Technology Areas

  • Directed Energy
  • Directed Energy - Lasers
  • Microelectronics
  • Quantum Computing