Additional structure in infrared excitation spectra of group-III acceptors in silicon

High-resolution infrared $p_{\frac{3}{2}}$ and $p_{\frac{1}{2}}$ excitation spectra are reported for the group-III acceptors boron, aluminum, gallium, and indium in silicon. New lines, which are believed to be due to previously unresolved excited states, are observed in the $p_{\frac{3}{2}}$ spectra. A $5p^{\prime }$ line is observed for the first time in the gallium spectrum. Some previously reported boron $p_{\frac{3}{2}}$ lines are relabeled to correspond with the other group-III spectra. A feature in each of the $p_{\frac{3}{2}}$ spectra is defined as $E_I$, the ground-state binding energy. Values measured for $E_I$ are 44.39, 69.03, 72.73, and 155.58 (±0.02) meV for B, Al, Ga, and In, respectively. The data show more complete correspondence between all the group-III excited-state lines than any previously published. The spin-orbit splitting of the valence bands is experimentally deduced to be 44.00±0.02 meV.