A Study on Epitaxial Lift-Off in InGaP/GaAs Double-Junction Solar Cells via Au-Au Bonding on Pre-Patterned Area

Abstract

We have investigated the improvement of GaAs substrate reusing and the regrowth possibility of the epi-layer for the flexible InGaP/GaAs double junction solar cell. The presence of residues on the GaAs substrate surface separated by the epitaxial lift-off process is closely related to the regrowth of the epitaxial layer. A pre-patterning process was introduced to investigate the correlation between the lateral etch rate of the sacrificial layer and the generation of residues on the substrate. And the lateral etch rate was adjusted according to the changes in the pre-patterning area. The residues on surface of the GaAs substrate according to the lateral etch rate were observed by SEM/EDX. The structure of the InGaP/GaAs double junction solar cell re-grown on the GaAs substrate was measured by X-ray diffraction. The performance of the re-grown solar cell was measured by the current density-voltage curve at AM1.5G, 1sun with a solar simulator. The GaAs substrate was separated in the cleanest state by the pre-patterning area of 2 x 2mm2, and the conversion efficiency of the re-grown solar cell by reusing this for three times was maintained similar to its conversion efficiency when a solar cell of initial growth.

Keywords

• Flexible solar cell
• epitaxial lift-off
• pre-patterning
• lateral etch rate
• substrate reusing