Phonon Engineered Materials for Fine-Tuning the G-R Center and Auger Recombination
Abstract
The development of the next generation of devices that enable advanced electro-optic detection, sensing and imaging requires innovative materials with controlled or strongly suppressed charge carrier recombination. The internal quantum efficiency of light-emitting diodes and laser diodes, defined as the fraction of the electron-hole pairs that recombine by emitting a photon, is reduced by various non-radiative recombination processes. Non-radiative recombination, which involves lattice defects and impurity atoms, is detrimental for many electro-optic devices used for sensing and imaging. Non-radiative recombination involves phonons, i.e. quanta of crystal lattice vibrations, for energy dissipation. Phonons with specific momentum and energy are needed to satisfy the conservation laws for the electron-hole recombination process to occur. In this project, we investigate a possibility of suppressing the phonon assisted recombination processes by engineering the phonon and electron density of states in specially designed crystal structures. Modification of the acoustic phonon dispersion in periodic arrays of nanostructures, e.g. quantum dots, can result in the emergence of gaps or peaks in the density of states in relevant wavelength intervals, thus affecting recombination rates in the processes requiring phonons for momentum conservation. The properties of specially designed nanostructures are investigated using a combination of experimental techniques: Brillouin-Mandelstam and micro-Raman light scattering spectroscopies, low-frequency electronic noise spectroscopy, photoluminescence and time-resolved luminescence spectroscopies. The charge carrier trapping-emission dynamics is studied using the low-frequency electronic noise measurements. The project outcomes include fabricated sets of periodic semiconductor crystal structures; measured low-frequency noise characteristics of the periodic arrays and reference samples; phonon spectra of quantum dot arrays; and charge-carrier recombination rates. The results of this proof-of-concept project have practical implications for the design of novel photodetectors, sensors, and light-emitting diodes.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 20, 2019
- Source ID
- W911NF1810041
Entities
People
- Alexander A. Balandin
Organizations
- Army Contracting Command
- Defense Advanced Research Projects Agency
- University of California, Riverside