Concentration Effects on the Line Spectra of Bound Holes in Silicon

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.