Infrared Radiative Properties of Heavily Doped Silicon at Room Temperature

This paper describes an experimental investigation on the infrared radiative properties of heavily doped Si at room temperature. Lightly doped Si wafers were ion-implanted with either boron or phosphorus atoms, with dosages corresponding to as-implanted peak doping concentrations of $1020$ and $1021cm−3$⁠; the peak doping concentrations after annealing are $3.1×1019$ and $2.8×1020cm−3$⁠, respectively. Rapid thermal annealing was performed to activate the implanted dopants. A Fourier-transform infrared spectrometer was employed to measure the transmittance and reflectance of the samples in the wavelength range from $2μm$ to $20μm$⁠. Accurate carrier mobility and ionization models were identified after carefully reviewing the available literature, and then incorporated into the Drude model to predict the dielectric function of doped Si. The radiative properties of doped Si samples were calculated by treating the doped region as multilayer thin films of different doping concentrations on a thick lightly doped Si substrate. The measured spectral transmittance and reflectance agree well with the model predictions. The knowledge gained from this study will aid future design and fabrication of doped Si microstructures as wavelength selective emitters and absorbers in the midinfrared region.