High-efficiency metamorphic GaInP/GaInAs/Ge solar cells grown by MOVPE

• Published in: Journal of crystal growth 2004-01, Vol.261 (2), p.341-348
• Main Authors: Fetzer, C.M., King, R.R., Colter, P.C., Edmondson, K.M., Law, D.C., Stavrides, A.P., Yoon, H., Ermer, J.H., Romero, M.J., Karam, N.H.
• Format: Article
• Language: English
• Subjects: A1. Metamorphic; A3. Metalorganic vapor phase epitaxy; Applied sciences; B1. GaInAs; B1. GaInP; B1. Germanium; B3. Solar cells; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Energy; Exact sciences and technology; Iii-v semiconductors; Natural energy; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Photoelectric conversion: solar cells and arrays; Photovoltaic conversion; Physics; Solar cells. Photoelectrochemical cells; Solar energy
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2003.11.026

This paper focuses on the metal-organic vapor-phase epitaxy growth of 3-junction (3J) solar cells where the epitaxial Ga 0.44In 0.56P top and Ga 0.92In 0.08As middle subcells are grown lattice-mismatched on a Ge substrate. Single-junction metamorphic devices with 8% and 12%-In, GaInAs are grown on 100 mm dia. (0 0 1) Ge substrates and evaluated in comparison to approximately lattice-matched GaAs and Ga 0.99In 0.01As subcells. Layers are observed to be nearly 100% relaxed by high-resolution X-ray diffraction. Threading dislocation densities of ∼2×10 5 cm −2 in the 8%-In layers are observed by electron beam induced current and cathodoluminescence. Single-junction devices show a constant offset between open-circuit voltage and bandgap of ∼380 mV. Building upon these results, 3J metamorphic Ga 0.44In 0.56P/Ga 0.92In 0.08As/Ge solar cells are fabricated. Very high performances of small area devices are reported with 28.8% efficiency under the AM0 spectrum and 31.3% efficiency under the AM1.5G 1-sun terrestrial spectrum.