Wafer-scale detachable monocrystalline Germanium nanomembranes for the growth of III-V materials and substrate reuse

Germanium (Ge) is increasingly used as a substrate for high-performance optoelectronic, photovoltaic, and electronic devices. These devices are usually grown on thick and rigid Ge substrates manufactured by classical wafering techniques. Nanomembranes (NMs) provide an alternative to this approach while offering wafer-scale lateral dimensions, weight reduction, limitation of waste, and cost effectiveness. Herein, we introduce the Porous germanium Efficient Epitaxial LayEr Release (PEELER) process, which consists of the fabrication of wafer-scale detachable monocrystalline Ge NMs on porous Ge (PGe) and substrate reuse. We demonstrate monocrystalline Ge NMs with surface roughness below 1 nm on top of nanoengineered void layer enabling layer detachment. Furthermore, these Ge NMs exhibit compatibility with the growth of III-V materials. High-resolution transmission electron microscopy (HRTEM) characterization shows Ge NMs crystallinity and high-resolution X-ray diffraction (HRXRD) reciprocal space mapping endorses high-quality GaAs layers. Finally, we demonstrate the chemical reconditioning process of the Ge substrate, allowing its reuse, to produce multiple free-standing NMs from a single parent wafer. The PEELER process significantly reduces the consumption of Ge during the fabrication process which paves the way for a new generation of low-cost flexible optoelectronics devices.Comment: 17 pages and 6 figures along with 3 figures in supporting informatio

Unraveling the Heterointegration of 3D Semiconductors on Graphene by Anchor Point Nucleation

International audienceAbstract The heterointegration of graphene with semiconductor materials and the development of graphene‐based hybrid functional devices are heavily bound to the control of surface energy. Although remote epitaxy offers one of the most appealing techniques for implementing 3D/2D heterostructures, it is only suitable for polar materials and is hugely dependent on the graphene interface quality. Here, the growth of defect‐free single‐crystalline germanium (Ge) layers on a graphene‐coated Ge substrate is demonstrated by introducing a new approach named anchor point nucleation (APN). This powerful approach based on graphene surface engineering enables the growth of semiconductors on any type of substrate covered by graphene. Through plasma treatment, defects such as dangling bonds and nanoholes, which act as preferential nucleation sites, are introduced in the graphene layer. These experimental data unravel the nature of those defects, their role in nucleation, and the mechanisms governing this technique. Additionally, high‐resolution transmission microscopy combined with geometrical phase analysis established that the as‐grown layers are perfectly single‐crystalline, stress‐free, and oriented by the substrate underneath the engineered graphene layer. These findings provide new insights into graphene engineering by plasma and open up a universal pathway for the heterointegration of high‐quality 3D semiconductors on graphene for disruptive hybrid devices

Sequential fabrication of multiple Ge nanomembranes from a single wafer: Towards sustainable recycling of Ge substrates

International audienc

Large‐Scale Formation of Uniform Porous Ge Nanostructures with Tunable Physical Properties

Abstract Porous germanium (PGe) nanostructures attract a lot of attention for various emerging applications due to their unique properties. Consequently, there is an increasing need for the development of low‐cost synthesis routes that are compatible with large‐scale production. Bipolar electrochemical etching (BEE) is a widely used solution for producing porous Ge layers. However, the lack of controllable production of large‐scale uniform PGe layers is the limiting factor for mainstream applications. Large‐scale homogeneous PGe layers formation is demonstrated by improving the BEE process. The PGe structures demonstrate excellent homogeneity in thickness and porosity, with a relative variation of below 2% across the 100 mm wafer. Furthermore, this process enables accurate tuning of the PGe's physical properties through variation of the etching parameters. PGe structures with porosity ranging from 40% to 80% and an adjustable thickness, while preserving low surface roughness are demonstrated, giving access to a large variety of PGe nanostructures for a wide range of applications. Ellipsometry and X‐ray reflectivity are employed to measure the porosity and thickness of PGe layers, providing fast and non‐destructive methods of characterization. These findings lay the groundwork for the large‐scale production of high‐quality PGe layers with on‐demand characteristics

Germanium Surface Wet-Etch-Reconditioning for Porous Lift-off and Substrate Reuse

Reducing both the cost and weight of Germanium (Ge)-based devices is a key concern in extending these technologies to mainstream applications. In this framework, the porous Ge liftoff, based on a mesoporous Ge layer (PGe), shaped by bipolar electrochemical etching (BEE), constitutes an appealing strategy allowing the separation of lightweight, flexible, and low-cost devices and substrate reuse. However, after the device detachment, the broken pillar residues on the host substrate's surface prevent its reuse. Here, we report on the development and application of a reconditioning process based on an aqueous HF:H 2 O 2 :H 2 O (10:80:10, v-v-v) mixture without the need for Chemical Mechanical Polishing (CMP). We found that a mixed kinetic-and diffusion-controlled wet etching leads to surface polishing. Flat reconditioned substrates wit

High‐efficiency GaAs solar cells grown on porous germanium substrate with PEELER technology

III‐V solar cells are mainly grown on GaAs or Ge substrate, which significantly contributes to the final cost and affects the sustainable use of these rare materials. We developed a so‐called PEELER process in which a porosification technique is used to create a weak layer between a Ge substrate and the epitaxial layers. This method enables the separation of the grown layers, allowing for the subsequent reuse of germanium and a reduction in the environmental and economic cost of optoelectronic devices. Technology validation using the device performance is important to assess the technology interest. For this purpose, we fabricated and compared the performance of 22 non‐detached single‐junction (s‐j) GaAs photovoltaic cells grown and manufactured on porosified 100mm Ge wafer without anti‐reflection coating (ARC). All the cells exhibit comparable performance to state‐of‐the‐art GaAs solar cells (grown or Ge or GaAs) with high efficiency (21.8% ± 0.78%) and thereby demonstrate the viability of growing high‐performance optoelectronic devices on detachable Ge films. This article is protected by copyright. All rights reserved