Date of Degree
PhD (Doctor of Philosophy)
Prineas, John P.
Boggess, Thomas F.
First Committee Member
Second Committee Member
Andersen, David R.
Third Committee Member
InAs/GaSb superlattices are an attractive material system for infrared light emitting diodes, due to the ability to tune the band gap throughout most of the infrared regime. A key consideration in the epitaxial growth of these heterostructures is crystalline material quality. In developing thick layers of epitaxially grown material, there are moderate amounts of elastic strain that can be incorporated into a heterostructure, beyond which deformations will form that will alleviate the lattice mismatch. This thesis investigates the optical and electronic properties of lattice-mismatched and strained materials through the study of thick dual-color light emitting diodes, broadband light emitting diodes, and InAs/GaSb superlattice devices developed on GaAs substrates and GaAs integrated circuits.
A dual-color infrared light emitting diode is demonstrated emitting in the mid-wave infrared band at 3.81 μm and 4.72 μm. The design of the device stacks two independently operable InAs/GaSb superlattices structures on top of one another, so that 10 μm of material is grown with molecular beam epitaxy. Each layer is lattice-matched to a GaSb substrate. At quasi-continuous operation, radiances of 5.48 W/cm2-sr and 2.67 W/cm2-sr are obtained.
A broadband light emitting diode spanning the mid-wave infrared is demonstrated with eight stages of InAs/GaSb superlattices individually tuned to a different color. The performance of the device is compared with an identical eight stage device emitting in the middle of the mid-wave infrared. The emission of the fabricated broadband device spans from 3.2 μm to 6 μm with peak radiance of 137.1 mW/cm2-sr.
Growth of antimonide-based devices on GaAs is desirable to the relative transparency of semi-insulating substrates throughout the infrared, and as semi-insulating GaSb substrates are not available. The growth of bulk GaSb on GaAs is explored through different techniques in order to confine relaxation due to lattice mismatch strain to the GaSb/GaAs interface. A low temperature nucleation technique with a thin GaSb wetting layer is found to have the best overall surface morphology, although screw dislocations are a prominent feature on all samples. The dislocations and overall surface roughness are not found to destructively impact the overall device quality, as four stage InAs/GaSb superlattice devices grown on GaAs substrates are found to have superior electroluminescent emission and external quantum efficiency compared to an identical device grown on a GaSb substrate due to the higher substrate transparency and superior thermal properties.
Epitaxy on electronics growth techniques on GaAs integrated circuits are developed to bypass the hybridization process in light emitting diode development. Chips obtained from Quorvo, Inc. are found to endure ultra-high vacuum molecular beam epitaxy environment at higher temperatures with silicon nitride encapsulation, and a low temperature oxide removal technique is developed using an atomic hydrogen source. Chemical-mechanical polishing techniques are developed to create an “epi-ready” substrate surface. Ultimately, no photoluminescent emission is observed from InAs/GaSb superlattices grown on GaAs integrated circuits, although electroluminescent emission is still possible.
GaAs, InAs/GaSb Superlattices, Light Emitting Diodes, Molecular Beam Epitaxy
xii, 127 pages
Includes bibliographical references (pages 113-127).
Copyright © 2016 Sydney R, Provence
Provence, Sydney R.. "Next generation mid-wave infrared cascaded light emitting diodes: growth of broadband, multispectral, and single color devices on GaAs and integrated circuits." PhD (Doctor of Philosophy) thesis, University of Iowa, 2016.