Project Hermes: Dual-Function Interlayer Architecture for GaN-on-Si Heteroepitaxy (Er2O3 as a Simultaneous Stress Buffer and Optical Emitter Enabled by the Angelica Framework)

This paper presents Project Hermes—a dual-function interlayer architecture for GaN-on-Si(111) heteroepitaxy based on erbium oxide (Er2O3) as the buffer material within the Angelica framework [1]. The core contribution is the first demonstration that a single interlayer material can simultaneously serve two fundamentally distinct functions: (1) mechanical stress buffering via the Angie’s Grading compositional profile [1], and (2) optical signal emission at 1.54µm—the minimum-loss window of global fibre-optic communication networks. Prior to the Angelica framework, the lattice mismatch between Er2O3 and Si (2.96%) prevented high-quality epitaxial growth and rendered its optical potential inaccessible. The Angelica asymmetric interface architecture provides the stable epitaxial platform that unlocks Er2O3’s dual functionality for the first time. Multi-physics simulation (modules v8–v16) yields the following results: residual thermal stress reduced from 1110MPa to 163.4MPa (−85.3%); cut-off frequency fT = 255GHz; maximum oscillation frequency fmax = 324GHz; noise figure NF=0.23dB at 28GHz; fatigue life 4.46×106 thermal cycles; optical crystal quality 85.3% of ideal. All RF and power targets are met or exceeded. The Er3+ characteristic emission at 1.54 µm is confirmed compatible with standard telecom fibre coupling, establishing a conceptual pathway toward monolithically integrated GaN/Er2O3 electro-optical devices. Keywords: GaN-on-Si, HEMT, Er2O3, erbium oxide, stress buffer, optical emitter, 1.54µm, C-band, electrooptical integration, Angie’s Grading, Angelica framework, heteroepitaxy, dual-function interlayer Version 2 updates: (1) Optical efficiency model corrected from first-order linear to SRH non-radiative recombination (η_emission = 49.5%, full system η = 0.20%); (2) GaN→Er³⁺ energy mismatch resolved via indirect band-to-band excitation mechanism (10³⁻⁵× direct); (3) Post-deposition anneal 600-800°C N₂ identified as mandatory process step unique to Hermes architecture.