Excitation Spectrum of Aluminum Acceptors in Diamond under Uniaxial Stress

A high-resolution survey of the 0.30-0.37-eV spectra, attributed to transitions at acceptor centers, obtained from several natural p-type semiconducting diamonds at 80^∘{}K, is presented. Effects on the spectrum of destruction of the normal site symmetry (Td) by uniaxial compression are described. Hydrostatic stress has also been applied. Large spectral changes produced by uniaxial stress in the range 0-30 kbar have been analyzed in terms of the effective-mass theory of weakly bound electronic states, the lowest transitions being between quasihydrogenic s-p-like states. A coupling scheme here introduced for the p-like states is the opposite to that obtained for Si and Ge. Assignment of transitions has been made using theoretical band structures, results of reported spectral changes between 80 and 5^∘{}K, and the present stress spectra. Analysis of stress effects has been made using deformation-potential theory. The resulting potentials of Dᵤᵛ=+2.47, Dᵤᵛ=+1.63 eV are of the same sign as and similar magnitude to those of silicon.