InGaP solar cell on Ge-on-Si virtual substrate for novel solar power conversion

Abstract

InGaP single-junction solar cells are grown on lattice-matched Ge-on-Si virtual substrates using metal-organic chemical vapor deposition. Optoelectronic simulation results indicate that the optimal collection length for InGaP single-junction solar cells with a carrier lifetime range of 2-5 ns is wider than approximately 1 lm. Electron beam-induced current measurements reveal that the threading dislocation density (TDD) of InGaP solar cells fabricated on Ge and Ge-on-Si substrates is in the range of 10 4 -3 Â 10 7 cm À2 . We demonstrate that the open circuit voltage (V oc ) of InGaP solar cells is not significantly influenced by TDDs less than 2 Â 10 6 cm À2 . Fabricated InGaP solar cells grown on a Ge-on-Si virtual substrate and a Ge substrate exhibit V oc in the range of 0.96 to 1.43 V under an equivalent illumination in the range of $0.5 Sun. The estimated efficiency of the InGaP solar cell fabricated on the Ge-on-Si virtual substrate (Ge substrate) at room temperature for the limited incident spectrum spanning the photon energy range of 1.9-2.4 eV varies from 16.6% to 34.3%.

Ge virtual substrates for high efficiency III-V solar cells: applications, potential and challenges

“…The expected TDD of the Ge/Si templates used, around 4•10 6 cm -2 , could be partly responsible of these results, but the comparison with inverted metamorphic 3JSC structures with similar TDD developed in our laboratory, and with GaAs and GaInP SJSCs grown on Ge/Si virtual substrates by other authors [5], [6], suggest that there must be additional causes. These could be linked to the mechanical instability of the semiconductor structure to temperature variations.…”

“…A two-step deposition process was presented almost two decades ago, which attained a TDD of 2·10 7 cm -2 and could be reduced down to 2.3·10 6 cm -2 using selective area growth [4]. More recently, the potential of these virtual substrates for the fabrication of high efficiency III-V solar cell has been experimentally demonstrated by growing GaAs and GaInP solar cells, with promising results [5], [6]. Given the thin Ge layers used (< 5 µm typically), this approach offers an attractive potential for low substrate cost and eases on material scarcity concerns.…”

Ultrathin Ge epilayers on Si produced by low-temperature PECVD acting as virtual substrates for III-V / c-Si tandem solar cells

“…This shall drastically reduce the cost of GaAs cells as the price of monocrystalline GaAs or Ge wafer is about 100-130 $ for a 6-inch wafer, while solar-grade c-Si wafer of the same size is about 0.5$ [6]. The lower cost of silicon wafers originates from the higher abundance of silicon in the earth's crust than germanium, the higher mechanical strength of c-Si, and the wellestablished processing technology of the silicon industry [6][7][8][9][10][11].…”

GaAsP/SiGe tandem solar cells on porous Si substrates

“…III-V/Si architectures have been demonstrated for optoelectronics with lasers (Groenert et al 2003), bipolar transistors (Lew et al 2007), photodetectors (Luan et al 1999) or light emitting diodes (Yang et al 2002). As for monolithic III-V/Si photovoltaic devices, GaAsP/Si dual junctions using GaP buffer layers (Hayashi et al 1994a, Lepkowski et al 2020, Fan et al 2020a, Fan et al 2020b, Fan et al 2019, Caño et al 2021, Saenz et al 2020, GaInP/GaAs tandem cells on Ge/Si virtual substrates (Ginige et al 2006, Wang et al 2017, Kim et al 2018, Bioud et al 2019 and…”