Role of hydrogen in hydrogen-induced layer exfoliation of germanium

Abstract

The role of hydrogen in the exfoliation of Ge is studied using cross-sectional transmission electron microscopy, atomic force microscopy, and multiple-internal transmission mode Fourier-transform infrared absorption spectroscopy and compared with the mechanism in silicon. A qualitative model for the physical and chemical action of hydrogen in the exfoliation of these materials is presented, in which H-implantation creates damage states that store hydrogen and create nucleation sites for the formation of micro-cracks. These micro-cracks are chemically stabilized by hydrogen passivation, and upon annealing serve as collection points for molecular hydrogen. Upon further heating, the molecular hydrogen trapped in these cracks exerts pressure on the internal surfaces causing the cracks to extend and coalesce. When this process occurs in the presence of a handle substrate that provides rigidity to the thin film, the coalescence of these cracks leads to cooperative thin film exfoliation. In addition to clarifying the mechanism of H-induced exfoliation of single-crystal thin Ge films, the vibrational study helps to identify the states of hydrogen in heavily damaged Ge. Such information has practical importance for the optimization of H-induced layer transfer as a technological tool for materials integration with these materials systems.

Low temperature exfoliation process in hydrogen-implanted germanium layers

“…Such hydrogen-filled cavities have been reported to be located at a depth between the hydrogen projected range 4 and the germanium vacancy range below the germanium surface. Lattice deformation induced by these cavities generates surface blisters which are optically visible ͑Fig.…”

“…The formation of these nanocracks is known to be limited by the breaking of Ge-H lattice bonds and by hydrogen diffusion. 4,16 The length of most of these cracks does not exceed 50 nm and their propagation causes minor lattice deformation ͓Fig. 2͑b͒͑2͔͒.…”

“…As temperature and/or anneal time increase, the internal pressure inside the blisters increases and results in the formation of microcracks which triggers the splitting of a thin semiconductor layer. 2,3 The mechanisms which govern defect formation in H-implanted semiconductors and the creation of microcracks has already been extensively characterized in silicon, germanium, 4 and III-V compounds. 5 It is often addressed from a wafer bonding perspective and targets a range of applications varying from the fabrication of low defective substrates for complementary metal-oxide-semiconductor compatible applications ͓͑SOI and germanium-on-insulator substrates "GeOI" ͑Ref.…”

Lattice Strain Measurements in Hydrogen Implanted Materials for Layer Transfer Processes

“…However, because of its higher weight, helium produces more defects in the lattice and bigger exfoliated area. Hydrogen is more often used for a lot of semiconductors such as Si (Höchbauer et al, 1999), Ge (Zahler et al, 2007), SiC (Malouf et al, 2005), InP (Aspar et al, 2001), .…”

GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates

“…7,8 The bonded templates were fabricated with wafer bonding and ion implantation induced layer transfer. 9,10 This technique allows careful control of transferred film thickness and guarantees high-quality single crystal thin films in direct contact with the handle substrate. This is in contrast to previous work to grow III-V devices on Si substrates, which required buffer layers to minimize the defect generation in the active devices.…”