• Scalable fabrication of uniform and defect free SGOI layer by Ge condensation. • High germanium concentration (85%) in ultrathin (5 nm) SGOI layer. • Ge concentration upper limit in SGOI substrate, produced by condensation process. • Industrial substrate fabrication for Ge and III-V semiconductors epitaxial regrowth. It was reported recently that hot condensation process can produce fully strained or relaxed Ge-rich (<50%) SiGe layers embedded in an oxide layer. However, higher germanium concentrations are requested to improve quantum efficiency and allow thinner absorbing layers, while maintaining compatibility with silicon-based technologies. In this work we report that a modified hot Ge condensation process is highly effective for the scalable fabrication of high-quality Silicon-Germanium-on-Insulator (SGOI) layers with high, critical germanium content (∼85%) on 300 mm wafers. Starting from thin epitaxial SiGe layers, the process employs sequential high-temperature oxidation stages under reduced oxygen partial pressure to incrementally enrich Ge concentration while preserving structural integrity. Two samples targeting ∼85% and ∼100% Ge content were investigated. The ∼85% Ge SGOI layer exhibits excellent crystalline quality, uniform Ge depth distribution, and partial compressive strain with no observable dislocations. Extending condensation to achieve near-pure Ge layer results in morphological instability, characterized by solid-state dewetting of the condensed layer and formation of monocrystalline pure Ge islands. Our findings identify ∼85% Ge as the practical upper limit for continuous, defect-free SGOI films via hot condensation on large-scale wafers. Beyond this threshold, strain relaxation via dewetting limits film uniformity and device applicability. These results provide critical insights for optimizing Ge condensation processes toward high-performance SGOI and Ge-on-Insulator (GOI) substrates for advanced CMOS applications.
Takala et al. (Sun,) studied this question.