Effect of pulsed laser annealing on optical properties of selenium-hyperdoped silicon

Layers of selenium-hyperdoped silicon with dopant concentration of up to (4–6) $\times$ 10$^{20}$ cm$^{-3}$ that exceeds the limit of equilibrium solubility of this impurity by 4 orders of magnitude were obtained using ion implantation followed by pulsed laser annealing (PLA) at pulse energy densities of $W$ = 0.55, 0.8, 1.0, 1.5, 2.0, and 2.5 J/cm$^2$. Rutherford back scattering of helium ions demonstrated that up to 60–70% of introduced impurity occupied silicon lattice sites. Selenium-hyperdoped layers exhibited substantial absorption (36–40%) in the wavelength range of 1100–2400 nm. Absorption spectra of silicon layers obtained at different regimes of laser annealing are compared with each other. It is demonstrated that annealing at $W$ = 2.0 J/cm$^2$ is optimal from the point of view of achieving maximum structural perfection of hyperdoped silicon layers. This factor is very important for application of formed structures in photodetectors and components of solar energy systems. At the same time, absorption in the visible and near IR wavelength ranges attained maximum value after annealing at $W$ = 1.0 J/cm$^2$ and remained nearly unchanged with further increase in the pulse energy density.