Wafer reuse for repeated growth of III–V solar cells

Abstract

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.

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

“…Post-chemical etching with thermal cleaning can potentially reduce the surface roughness to the level of the original wafer. However, the remaining contaminants still seriously degrade the quality of regrown films and device performances 9 . To completely remove all these contaminants and achieve high quality regrown films, multi-step chemical polishing with different sacrificial (protection) layers was recently proposed, with the penalties of the higher cost for extra epitaxial growths and HF still being used as the main etchant 19 .…”

“…Subsequently, this same method has been applied by many researchers to successfully peel GaAs thin films from the parent substrates and transfer them onto desirable substrates for various applications 7,8 . The major drawback of this method arises from the high surface roughness of the parent substrate as well as reaction residues left on the substrate after the ELO process, and post-process steps, for example, chemicalmechanical-polish or chemical etching, typically required to reclaim the substrate 9 . In addition, HF is a lethal and highly corrosive acid requiring special handling and extra protection.…”

Photovoltaic Concentrators - Fundamentals, Applications, Market & Prospective

“…From the manufacturing point of view, molecular organic chemical vapour deposition (MOCVD) equipments, industrially used for the epitaxial growth of the compound layers have been developed for high productivity. On the other side, different ways to reduce the cell cost replacing the Germanium or GaAs substrate with cheaper Silicon wafers (Archer et al, 2008) or using peeling-off techniques (Bauhuis, 2010) in order to use the same substrate for different growth have been investigated.…”

Temperature-Induced Degradation of Thin-Film III–V Solar Cells for Space Applications

“…First a flexible handle was applied to the thin-film solar cell structures after which they were removed from their growth substrates either by epitaxial lift-off [12] or by substrate etching with a 5:1 citric acid (1 kg in 1 kg H 2 O) : H 2 O 2 (32%) solution. After substrate removal the cell structures were transferred to a ∼ 20 µm Au mirror/back contact/carrier or to a ∼ 25 µm Cu carrier with a 100 nm Au mirror/back contact (the Au acts as a photon confining mirror [36]- [39]) and then mounted on a temporary glass carrier for further processing.…”

“…Techniques such as epitaxial lift-off (ELO) [6]- [9] and controlled spalling [10], [11] allow for substrate removal without destruction of the expensive growth substrate, thus allowing for substrate re-use [12], [13]. The released active cell structures have the intrinsic potential to be turned into genuine thin-film devices if they are transferred to a thin and flexible carrier.…”