High efficiency GaAs thin film solar cells by peeled film technology

Konagai, Makoto; Sugimoto, M.; Takahashi, Kiyoshi

doi:10.1016/0022-0248(78)90449-9

Cited by 302 publications

(175 citation statements)

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“…This is of particular importance for an intrinsically large area, thus expensive devices like high efficiency III/V solar cells, 2,3 and the integration of III/V based components with, e.g., silicon-based devices. 4,5 Recently, at our institute thin-film GaAs solar cells were made based on the ELO technique, which reached record efficiencies of 24.5%.6 This is close to the highest efficiency of 25.1% reported for regular GaAs cells on a GaAs substrate, 7 which indicates that the ELO process is not detrimental to the quality of the thin-film device.In 1978 Konagai et al 8 described the separation of devices from a GaAs substrate using the extreme selectivity of hydrofluoric acid ͑HF͒ for Al x Ga 1−x As with a high Al fraction. A wax layer was applied to support the 30 µm thick fragile films during the process.…”

mentioning

confidence: 99%

A Diffusion and Reaction Related Model of the Epitaxial Lift-Off Process

Niftrik

Schermer

Bauhuis

et al. 2007

J. Electrochem. Soc.

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In the present work a so-called diffusion and reaction related model ͑DR model͒ is derived based on the notion that the overall etch rate in the epitaxial lift-off ͑ELO͒ process is determined both by the diffusion rate of hydrofluoric acid to the etch front and its subsequent reaction rate in the process. In contrast to the model that was previously described in the literature, the DR model yields etch rates which are in quantitative agreement with those obtained experimentally. In order to verify the DR model, the ELO etch rate of AlAs 1−y P y release layers is determined as a function of the phosphorus percentage, the release layer thickness and the temperature. In accordance with the DR model, it is shown that the etch rate is reaction rate related by the dependence on the phosphorus percentage in the release layer, and that the etch rate is diffusion rate related by the dependence on the release layer thickness. From the temperature dependence, an activation energy of 0.31 eV could be deduced for the ELO process under the present conditions. © 2007 The Electrochemical Society. ͓DOI: 10.1149/1.2779968͔ All rights reserved. The "epitaxial lift-off" ͑ELO͒ technique ͑see Fig. 1a͒, in which a III/V device structure is separated from its GaAs substrate by using selective wet etching of a thin Al x Ga 1−x As ͑x Ͼ 0.6͒ release layer and transferred to a foreign carrier, allows the production of singlecrystalline thin films of III/V materials.1 Application of this technique is interesting for the optoelectronics industry, because use of thin-film devices potentially results in a more efficient transfer of generated heat from device to carrier or heat sink and significantly reduces the amount of material needed by reuse of the substrates. This is of particular importance for an intrinsically large area, thus expensive devices like high efficiency III/V solar cells, 2,3 and the integration of III/V based components with, e.g., silicon-based devices. 4,5 Recently, at our institute thin-film GaAs solar cells were made based on the ELO technique, which reached record efficiencies of 24.5%.6 This is close to the highest efficiency of 25.1% reported for regular GaAs cells on a GaAs substrate, 7 which indicates that the ELO process is not detrimental to the quality of the thin-film device.In 1978 Konagai et al. 8 described the separation of devices from a GaAs substrate using the extreme selectivity of hydrofluoric acid ͑HF͒ for Al x Ga 1−x As with a high Al fraction. A wax layer was applied to support the 30 µm thick fragile films during the process. Yablonovitch et al. 9 noted that the tension induced by the wax caused the thinner films, of micrometer thickness, to curl up with a radius of curvature r as they became undercut. This was concluded to be beneficial for removal of the etch products, leading to an increased lateral etch rate V e of the AlAs release layer. By assuming that three moles of hydrogen ͑H 2 ͒ gas are produced for each mole of AlAs etched and that the ability of dissolved H 2 , which has a low solubil...

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mentioning

confidence: 99%

A Diffusion and Reaction Related Model of the Epitaxial Lift-Off Process

Niftrik

Schermer

Bauhuis

et al. 2007

J. Electrochem. Soc.

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“…The attack of the substrate by the HF and the residues formed during the sacrificial layer etching result in the increase of RMS roughness from 0.3 to 1-4 nms range. Chemical reactions between AlAs and HF have been well studied 10,15,16 6 À n ] (3 À n) þ , on the other hand, are solid and hard to dissolve into the solution. Besides these primary byproducts, solid As 2 O 3 can also be generated on the substrate depending on the oxygen concentration of the etchant 17 .…”

Section: Resultsmentioning

confidence: 99%

“…In 1978, Konagai et al 6 proposed a method which is known today as epitaxial lift-off (ELO) to separate a device layer from a GaAs substrate by using hydrofluoric acid (HF) to selectively etch a AlGaAs (aluminium compound) sacrificial layer inserted between the device film and the substrate ( Fig. 1(a)).…”

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confidence: 99%

Epitaxial lift-off process for gallium arsenide substrate reuse and flexible electronics

et al. 2013

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Epitaxial lift-off process enables the separation of III-V device layers from gallium arsenide substrates and has been extensively explored to avoid the high cost of III-V devices by reusing the substrates. Conventional epitaxial lift-off processes require several post-processing steps to restore the substrate to an epi-ready condition. Here we present an epitaxial liftoff scheme that minimizes the amount of post-etching residues and keeps the surface smooth, leading to direct reuse of the gallium arsenide substrate. The successful direct substrate reuse is confirmed by the performance comparison of solar cells grown on the original and the reused substrates. Following the features of our epitaxial lift-off process, a high-throughput technique called surface tension-assisted epitaxial lift-off was developed. In addition to showing full wafer gallium arsenide thin film transfer onto both rigid and flexible substrates, we also demonstrate devices, including light-emitting diode and metal-oxidesemiconductor capacitor, first built on thin active layers and then transferred to secondary substrates.

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“…While recordhigh IQEs have been reported for devices fabricated on GaAs, 2 fabricating efficient LEDs typically requires lifting off 12,13 the GaAs substrate. On the other hand, the InGaAsP material system readily allows the fabrication of a thick lattice matched DHJ structure on a transparent InP substrate.…”

Section: Yield and Leakage Currents Of Large Area Lattice Matched Inpmentioning

confidence: 99%

Yield and leakage currents of large area lattice matched InP/InGaAs heterostructures

Olsson¹,

Aierken²,

Jussila³

et al. 2014

Journal of Applied Physics

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Demonstrating and harnessing electroluminescent cooling at technologically viable cooling powers requires the ability to routinely fabricate large area high quality light-emitting diodes (LEDs). Detailed information on the performance and yield of relevant large area devices is not available, however. Here, we report extensive information on the yield and related large area scaling of InP/InGaAs LEDs and discuss the origin of the failure mechanisms based on lock-in thermographic imaging. The studied LEDs were fabricated as mesa structures of various sizes on epistructures grown at five different facilities specialized in the growth of III-V compound semiconductors. While the smaller mesas generally showed relatively good electrical characteristics and low leakage current densities, some of them also exhibited unusually large leakage current densities. The provided information is critical for the development and design of the optical cooling technologies relying on large area devices.

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High efficiency GaAs thin film solar cells by peeled film technology

Cited by 302 publications

References 4 publications

A Diffusion and Reaction Related Model of the Epitaxial Lift-Off Process

A Diffusion and Reaction Related Model of the Epitaxial Lift-Off Process

Epitaxial lift-off process for gallium arsenide substrate reuse and flexible electronics

Yield and leakage currents of large area lattice matched InP/InGaAs heterostructures

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