The effect of impurity concentration on the line spectra of holes bound to B, Al, and Ga acceptors in silicon has been studied at 21°K. Details of the spectra (i.e., relative positions, line shapes, intensities) differ for the different acceptors. Below an acceptor concentration of about ${10}^{16}$/${\mathrm{cm}}^3$ the spectra are concentration-independent under the conditions of measurement. Above ${10}^{16}$/${\mathrm{cm}}^3$ the spectral lines begin to broaden and by ∼${10}^{18}$/${\mathrm{cm}}^3$ the line structure has been almost completely destroyed. A qualititive discussion of the concentration effects is given.

• Received 26 March 1956

DOI:https://doi.org/10.1103/PhysRev.103.103