Optical Science and Engineering ETDs

Publication Date

Summer 7-26-2019


GaSb based photovoltaic devices have been demonstrated on GaAs substrates by an inducing interfacial array of 90° misfit dislocations. Despite the beneficial qualities of the highly stable 90° misfit dislocation, there is a significant density of residual threading dislocations in the GaSb layer, resulting in the degradation of the electrical performance of such photovoltaic cells compared to lattice matched devices. We aim to reduce threading dislocation density by optimizing growth temperature and by using an AlSb dislocation filtering layer. The growth temperature optimization results in a reduction of the threading dislocation density to 1.3 × 108 cm−2. Adding an AlSb dislocation filtering layer further improves the electrical performance of the GaSb solar cells by reducing the threading dislocation density to 4 × 107 cm−2. A comparison between the experimental data and theoretical calculation confirms that the recombination in dislocation centers is a dominant loss mechanism in GaSb solar cell grown on GaAs substrate. Also, the band offset between AlSb/GaSb is not proper for photovoltaic application and block the photogenerated carrier to reach a contact. InGaSb strained layer was chosen as replacement of AlSb defect filtering layer. Effect of strain, thickness, and a number of InGaSb defect filtering layer on the electrical performance of GaSb photovoltaic cell grown on GaAs was tested. Strain, thickness and number of defect filtering layer optimization results in improvement of normalized open circuit voltage from 43% to 77% and short circuit current from 59% to 78% of GaSb photovoltaic cell.

Degree Name

Optical Science and Engineering

Level of Degree


Department Name

Optical Science and Engineering

First Committee Member (Chair)

Ganesh Balakrishnan

Second Committee Member

Adam Hecht

Third Committee Member

Payman Zarkeh-Ha

Fourth Committee Member

Francesca Cavallo


IMF, Photovoltaic, Thermophotovoltaic, GaSb, Defect filtering, Threading dislocation

Document Type