A Simple Model for Impurity Photoabsorption in Silicon

A simple model for absorption of infrared radiation by impurity atoms in silicon crystals has been developed and applied to electronic excitations ofthe Group V donors Bi, Sb, As, and P, and the Group III acceptors B, AI, Ga, and In. The model is based on the quantum-defect method for approximating bound donor or acceptor wave functions outside the core region of the impurity. For each donor species, the relative oscillator strengths have been calculated for the transitions from the ground state to the first four excited levels. For each acceptor species, the relative oscillator strengths were calculated for transitions from the P _3/2 ground state to the first three P _1/2 excited levels. Comparison with high-resolution absorption spectra show qualitative agreement for the low-lying transitions.