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The distribution of grown-in nitrogen-vacancy pairs in synthetic Ib diamond crystals has been imaged by means of a new photoluminescence tomographic technique. Using this method, local changes in luminescence intensity introduced by these defect centers were mapped by means of a laser-scanning microtomographic arrangement. It was found that the spatial variation in nitrogen-vacancy pair concentrations within a crystal qualitatively correlates with the nitrogen impurity distribution.

We have calculated the expressions for band-to-band luminescence given by Lasher and Stern for heavily doped GaAs. The resulting values in the case of no k selection rule are tabulated. A comparison between theory and experiment is made, which shows that good agreement can be obtained. From this comparison can be concluded that the band-to-band luminescence in heavily doped n-type GaAs is governed by transitions without k selection, whereas in moderately doped GaAs the transitions are without k selection at low temperatures but with k selection at room temperature.

We report the observation of 2p0,−1, 2s0, 3d−1,−2, 3p−1, and 4f−3 structures in the ‘‘two electron’’ satellite photoluminescence of excitons bound to the (hydrogenic) shallow donors Ge and Se/Sn in high purity metalorganic vapor-phase epitaxy grown GaAs. The attribution is based upon selective excitation of the different principal donor bound exciton (D0,X) lines at magnetic fields of 7 T at T=1.5 K, combined with a careful analysis of the behavior of the hydrogen atom in a magnetic field. The results are interpreted in terms of high magnetic field quantum numbers and in terms of shapes of hydrogen wavefunctions in strong magnetic fields. One of the samples used in this work is so pure that for the first time donors have been identified from the relatively broad n=2 two electron satellite involving the (D0,X) ground state at zero field.