Hyperdoping of Ge/Si and SiGe/Si epitaxial layers by UV-nanosecond laser processing

Hyperdoping group-IV semiconductors beyond equilibrium solubilities is crucial for advanced applications including nanoelectronics, photonics, plasmonics, and quantum computing. However, this process presents significant challenges due to solubility limits and dopant-defect interaction issues. In this study, we demonstrate that using UV nanosecond pulsed laser melting significantly enhances the phosphorus active concentration in insitu doped Ge/Si and Si0.15Ge0.85/Si layers. In Ge/Si layers we show that, by properly tuning the laser energy density, flat electron concentration depth profiles up to the record value of 2.5 x 1020 cm(-3) over considerable thicknesses of 300 nm are achieved, with 80 % active fraction, excellent surface morphology and optical properties with plasma wavelength down to 3 mu m. Notably, in this extreme hyperdoped regime, electron mobility deviates from previously reported trends and further decreases when the active P fraction drops below 30 %, due to carrier scattering from inactive P clusters. In Si0.15Ge0.85/Si layers, the maximum active concentration is 5 x 1019 cm(-3), with a 40 % active fraction and lower mobilities, consistent with literature data at lower doping levels. These results provide new insight into the electrical and optical properties of Ge and SiGe under hyperdoping conditions and support their potential integration in advanced mid-infrared photonic platforms, where flat, hyperdoped thick layers are essential.