The infrared-absorption spectra of a selection of aluminum-doped and nominally boron-doped semiconducting synthetic diamonds have been measured from 1 to 10 μ at temperatures near 100° and 300°K. These spectra are shown to be very similar to those obtained from natural semiconducting diamond. For large neutral-acceptor concentrations (${10}^{17}$ to ${10}^{19}$ ${\mathrm{cm}}^{-3\mathrm{}}$), line-broadening effects comparable with those reported in Si have been observed. An additional absorption feature has been found at 0.268 eV, and a tentative explanation of the transition involved is discussed.

• Received 25 June 1965

DOI:https://doi.org/10.1103/PhysRev.140.A1272