Runnan Zhang

We present a spectroscopic ellipsometry-based optical method for non-invasive, in situ electric field characterization via the absorption tail. The key advance is a reduction of the fitting problem from multiple free parameters to the reduced parameter by exploiting the intrinsic equivalence between the broadening factor γ and the space-charge region width L : for sufficiently large L (>90 nm), γ converges to zero. Unlike conventional Franz-Keldysh (FK) oscillation methods that require modulation spectroscopy and are restricted to wide, uniform fields, the absorption tail analyzed here persists under all field configurations—narrow or wide, uniform or non-uniform—making the approach universally applicable. Validated on three Si-doped GaN single crystals spanning carrier densities from 1.40 × 10 ¹⁷ to 3.20 × 10 ¹⁸ cm ⁻³ , the method achieves a reduction in root mean square error up to 68.7%±41.2% compared to traditional multi-parameter approaches via Raman, KPFM, and ellipsometry. Requiring only standard broadband ellipsometry, the method is material-general and inherently compatible with external optical, electrical, and magnetic stimuli, establishing a practical platform for in situ optical field diagnostics in semiconductor and photonic devices.

The potential of diamond films for future semiconductor applications is partly limited by current growth techniques. This limitation can be addressed by achieving an atomic-level understanding of the growth processes. Using atomic force microscopy with atomic resolution, we examined diamond surfaces and observed specific structures, where odd numbers of dimers form ribbonlike configurations. Formed in the nonequilibrium environment of plasma, these structures were evaluated as the most stable configurations through density-functional-theory calculations. Our findings provide a crucial foundation for optimizing the film growth process.