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Dissertation
Exotic superlattices and efficiency improvements for next generation infrared light emitting diodes
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2019
DOI: 10.17077/etd.005965
Abstract
InAs/GaSb superlattices have found great success as a platform for mid-infrared light-emitting diodes (LEDs). However, even these state-of-the-art LEDs have severely limited power conversion efficiencies, typically <1%. The ~99% of input power that is dissipated as heat further limits the device performance due to temperature dependent loss mechanisms such as Auger recombination. This thesis concentrates on three tasks: quantifying the amount of power lost to various loss mechanisms within the LED, mitigating the effects of loss-induced-heating, and reducing the amount of power lost to non-radiative recombination within the superlattice active region.
The different loss mechanisms within an LED are analyzed, and the fraction of power dissipated through each mechanism is computed. The interplay between Ohmic and quantum defect power losses are further examined in the context of LEDs comprising n-type anode layers, demonstrating the value of the fractional loss analysis method for future device optimizations. The n-type anode LEDs exhibited radiances of 6.7W/cm$^2$/sr from a 24$\mu$m$\times$24$\mu$m LED based on 16 cascaded InAs/GaSb superlattice at 77K, the highest report LED radiance to date for the midwave infrared.
Growth of InAs/GaSb superlattice LEDs on Si substrates was used to reduce the effects of device heating. Heterovalency and lattice-mismatch issues were alleviated by the use of vicinal substrates and migration enhanced epitaxy, respectively. Identical LED structures were grown on both native GaSb and foreign Si substrates and compared at 77K. Devices on Si outperformed devices on GaSb, except in low injection regimes where Shockley-Read-Hall dominated and exceedingly high injection where device failure became problematic.
New superlattices beyond InAs/GaSb were explored for increased quantum effciency in efforts to reduce the power lost to non-radiative recombination. Photoluminescence samples comprising a variety of InAs/GaSb, InAs/AlGaInSb, InAs/GaInSb/InAs/AlAsSb, GaInSb/InAs/GaInSb/AlAsSb, and InAs/InAsSb superlattice active regions were grown and characterized at 77K. The internal quantum effciency was determined without invoking the ABC model. Peak internal quantum effciencies ranged from 8% and 77%, a 2.5$\times$ improvement over the 29% peak internal quantum efficiency for an 8/16ML InAs/GaSb superlattice.
Details
- Title: Subtitle
- Exotic superlattices and efficiency improvements for next generation infrared light emitting diodes
- Creators
- Aaron Joseph Muhowski
- Contributors
- John P Prineas (Advisor)Fatima Toor (Committee Member)Craig Pryor (Committee Member)Markus Wohlgenannt (Committee Member)Jonathon Olesberg (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Physics
- Date degree season
- Autumn 2019
- Publisher
- University of Iowa
- DOI
- 10.17077/etd.005965
- Number of pages
- xv, 131 pages
- Copyright
- Copyright 2019 Aaron Joseph Muhowski
- Language
- English
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 123-131)
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984124361302771
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