George Higgins Hutchinson — Lei WangSimone Šuran Brunelli — Jonathan Klamkin, PhD.
Slides source: gitlab.com/geohh/aim
August 12, 2018
Development and Startup of a Micro-Photoluminescence Setup for Semiconductor Characterization and Optimization of Growth
Parameters
Wat lies beneath?
2/15
Photonic Integrated Circuits (PIC): Improved LiDAR, etc.PIC:▶ Small▶ Low cost▶ No moving parts
Discrete Optics/Electronics:▶ Large▶ Expensive▶ Multiple moving parts
Image credit: NASA/W. Hrybyk, https://www.nasa.gov/feature/goddard/2016/
nasa-engineers-tapped-to- bui ld-first-integrated-photonics-modem 3/15
Metal Organic Chemical Vapor Deposition (MOCVD):Motivation and Theory
Figure: MOCVD process, building up anInP crystal from Indium and Phosphideprecursors as organic byproducts escape
▶ PIC require lasers,waveguides, detectors
▶ Silicon unsuitable forlasers
▶ MOCVD to buildIII-V crystals forlasers
4/15
Characterization Techniques for Semiconductor Materials
MOCVD requires calibration to grow crystals of precisecomposition.How do we measure out growths to improve future runs?
Separationbetween atoms in
crystal
X-RayCrystalography
Morphology,topography,
parasitic growths
Atomic ForceMicroscopy
Band gap energy(of direct band
gap crystal)
PhotoluminescenceSpectroscopy
5/15
Photoluminescence Spectroscopy — Theory
Laser Sample
Monochromator Photodiode array
λ p
many wavelengths
λ l ± δ
1. Laser excites sample electrons2. Sample emits light3. Monochromator removes unnecessary wavelengths4. Photodiode array counts photons at specific wavelengths
6/15
Photoluminescence Spectroscopy — Motivation
Figure: 1.5µm InGaAsP laserschematic, adapted from Q. Ke etal.
▶ My research goal: configurea PL setup
▶ Observing band gap helpsinterpolate actual crystalcomposition
7/15
My Experimental
Laser
Sample
Monochromator
Photodiode Array
8/15
PL Setup: Software Development Problems and Techniques
Lack ofequipment
documentationNeed for future
modifibility
Reverse-engineering driversand example code
Object-orientedabstract device
structure
Need forlong-termstability
Dependencymanagement
tools
9/15
“Good” and “Bad” Quantum Dots under PL
“Good” dots:Tight size distribution, PL
“Bad” dots:Wide size distribution, PL.
10/15
Complex structures: multiple PL peaks
Substrate
Waveguide
CladdingQuantum Wells
Cladding
1180nm peak: Waveguide? 1300nm peak: Laser?
11/15
Structures respond differently to pump intensity changes
12/15
Conclusions — A Work in Progress
Hardware:▶ Photodetector: “It’s dead,
Jim.”▶ Identified potential
replacements▶ Contacted suppliers for
quotes
▶ Defective lasers troubleshot& replaced
Software:▶ Developed experimental
software for available parts▶ Software development
techniques to maximizehardware modularity
13/15
Future Work
▶ Short Term: Replace Photodetector▶ Develop software for data acquisition/analysis
▶ Long Term: Add mapping functionality▶ Motorized stage control▶ Adapt data acquisition/analysis software for mapping
14/15
Acknowledgments
15/15
Bowers group, for providing the PL setup used in ̀ `Identifying Structures based on PL Peaks'' data collection.
This material is based on research sponsored by Air Force Research Laboratory under agreement number FA8650-15-2-5220. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon .
The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of Air Force Research Laboratory or the U.S. Government.
