The Influence of InxGa1–xAs and GaAs1–yPy Layers Surrounding the AlAs Release Layer in the Epitaxial Lift-Off Process

Niftrik, A.T.J. van; Schermer, J.J.; Bauhuis, G.J.; Deelen, J. van; Mulder, P.; Larsen, P.K.

doi:10.1021/cg0700061

Cited by 8 publications

(10 citation statements)

References 42 publications

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“…At this composition the AlAs 1−y P y layer is almost lattice matched with the surrounding GaAs layers, thus it can be concluded that the maximum etch rate is obtained for an almost unstrained release layer. This correlates well with the fact that in previous work 13 it was observed that the ELO etch rate maximizes for layer structures with the least amount of strain in the two In x Ga 1−x As or two GaAs 1−y P y layers surrounding the AlAs release layer. This dependence of the lateral etch rate on the strain in the release layer structure is a strong indication that under these conditions the ELO process is hampered by reaction rate limitations.…”

Section: Discussionsupporting

confidence: 91%

“…In the actual experiments, however, much larger etch rates of several mm/h were obtained. [11][12][13] Nevertheless, the experiments 11 did show qualitatively the predicted linear relation between V e and h −0.5 , indicating that at least under some conditions diffusion does play a limiting role in the etch process. On the other hand, there is also experimental evidence that points to a reaction rate related process.…”

mentioning

confidence: 90%

“…A more detailed description of the process can be found in previous work. 13 After etching, the samples were rinsed in nanopure water and delicately blown dry with nitrogen. For each composition, thickness and etch temperature of the release layers 5-7 samples were processed to determine the average lateral etch rate and corresponding standard deviation.…”

Section: D630mentioning

confidence: 99%

“…This roughness is similar to that of the GaAs wafer before growth. 13 In previous work, 15 it was shown that AlF 3 ·3H 2 O is the only solid reaction product of the AlAs reaction with HF ͑see Eq. 3͒.…”

Section: ͓15͔mentioning

confidence: 99%

“…It was, for example, found that the etch rate could be varied significantly by the introduction of strain to the system. The strain could either be applied using an external force ͑bending the sample during etching 14 ͒ or an intrinsic force ͑application of strained layers surrounding the AlAs release layers 13 ͒. In the present work a model is derived based on the idea that the overall etch rate in the ELO process is determined both by the diffusion rate and the subsequent reaction rate of a certain species in the process.…”

mentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 91%

mentioning

confidence: 90%

Section: D630mentioning

confidence: 99%

Section: ͓15͔mentioning

confidence: 99%

mentioning

confidence: 99%

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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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Wafer reuse for repeated growth of III–V solar cells

Bauhuis

Mulder

Haverkamp

et al. 2010

Progress in Photovoltaics

112

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The epitaxial lift-off (ELO) technique can be used to separate a III-V solar cell structure from its underlying GaAs or Ge substrate. ELO from 4-inch Ge wafers is shown and 2-inch GaAs wafer reuse after lift-off is demonstrated without degradation in performance of the subsequent thin-film GaAs solar cells that were retrieved from it. Since a basic wet chemical smoothing etch procedure appeared insufficient to remove all the surface contamination, wafer re-preparation is done by a chemo-mechanical polishing procedure.

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