Epitaxial Lateral Overgrowth of GaAsP for III‐V/Si‐Based Photovoltaics

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2023-04, Vol.220 (8), p.n/a
• Main Authors: Strömberg, Axel, Manavaimaran, Balaji, Srinivasan, Lakshman, Lourdudoss, Sebastian, Sun, Yan-Ting
• Format: Article
• Language: English
• Subjects: Chemical-mechanical polishing; Electrical properties; Epitaxial growth; epitaxial lateral overgrowth; GaAsP/Si; Gallium arsenide; Gallium arsenide phosphide; hydride vapor-phase epitaxy; Photoluminescence; Photovoltaic cells; Silicon substrates; Solar cells
• ISSN: 1862-6300; 1862-6319; 1862-6319
• DOI: 10.1002/pssa.202200623

GaAsP/Si with high crystalline quality fabricated by cost‐effective heteroepitaxial technology is a promising pathway for realizing low‐cost Si‐based tandem solar cell with efficiency higher than 30%. Herein, hydride vapor‐phase epitaxy is used to perform selective area growth of GaAsP with high lateral coverage, referred to as epitaxial lateral overgrowth (ELOG). The ELOG is performed on GaAs‐based substrates as a prestudy, followed by GaAs/Si and GaAsP/Si seed wafers employing chemical mechanical polishing to fabricate full 2″ GaAsP/Si templates. These are subsequently used to grow and process GaAsP/Si pn‐junction structures for electrical characterization. The ELOG GaAsP is studied by spatially resolved photoluminescence (PL) mapping and high‐resolution X‐ray diffraction measurements. PL analysis of the GaAsP/GaAs ELOG samples reveals an enhanced P‐incorporation during lateral growth of GaAsP. This is also observed for the GaAsP/Si ELOG templates along with evidence of improved material quality, clearly distinguishing the laterally grown GaAsP from the planar growth directly above the Si substrate. Leakage pathways causing reduced electrical performance of the ELOG GaAsP/Si pn‐junction structures are identified. Defect reduction in heteroepitaxial GaAsP/Si growth is investigated by epitaxial lateral overgrowth in hydride vapor‐phase epitaxy. GaAsP pn junction is grown on ELOG GaAsP/Si after chemical mechanical polishing. The impact of defects on GaAsP pn junction on Si is examined. With further optimization of ELOG layer thickness and wafer processing, ELOG GaAsP/Si is promising for high‐efficiency photovoltaics.