Analysis of materials properties of thin film structures for thermoelectric and thermophotovoltaic applications

Metal-organic chemical vapor deposition (MOCVD) was used to grow InAsP graded layers and AlAs/GaAs superlattices for materials studies related to thermophotovoltaics and thermoelectrics respectively. High resolution x-ray diffraction (HRXRD) was used to determine the As concentration in each of the InAsP layers. Arsenic concentration was found to vary linearly with the percentage of AsH3 in the reactive gas flow up to 60 % deposited, and had an asymptotic relationship for higher incorporated concentrations. Higher growth temperatures reduced As incorporation. Transmission electron microscopy (TEM) images were used to determine layer thicknesses. The growth rate of InAsP layers was found to be independent of growth temperature and the percentage of As. Superlattice samples with 0 %, 5 %, 10 %, and 20 % variations in the superlattice period were grown via MOCVD and analyzed using HRXRD. The intensities of the satellite peaks were found to decrease and broaden with increasing variation in the period length and disappeared completely in samples with up to 10 % variation. Thermal conductivity measurements performed using an optical pump-probe technique showed lower thermal conductivities for samples with greater variation. The irregularity of the superlattice period is believed to enhance the structure's ability to impede phonon propagation.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Baum, Brian K

Advisor dc:contributor.advisor

• Eugene A. Fitzgerald.

• Materials Science and Engineering.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/112501

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/112501