Luminescence Studies of Oxygen‐Related Defects In Aluminum Nitride

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Abstract
Aluminum nitride possesses a unique ability to accommodate oxygen via lattice dissolution to levels exceeding 4 at.%. The mechanism for this large accommodation of oxygen is of technological and scientific interest due to the established delecterious effects of oxygen on the thermal conductivity in this material. When doped with oxygen, AlN exhibits an intense, very broad (FWHM > 1 eV), luminescence peak in the near‐UV (∼ 375 nm). Though there is little doubt that this transition is associated with oxygen incorporation in the lattice, both the anomalous width of this feature and the specific complex from which it is derived have been a matter of debate. This paper reviews past studies of the luminescence of oxygen‐related defects in AlN and presents recent detailed photoluminescence experiments which delineate changes in the luminescence as a function of oxygen content. These data are utilized in conjunction with other measurements to elucidate the nature of the oxygen‐related defect and its evolution as a function of oxygen concentration. A defect‐cluster model is presented which accounts for a transition in the luminescent properties of AlN and is found to be in accord with measurements on thermal conduction and unit‐cell volume changes in AlN. This understanding of the oxygen‐related defect in AlN from the photoluminescence studies is then utilized in cathodoluminescence studies via cathodoluminescence imaging in a scanning electron microscope and a transmission electron microscope. Such techniques are extremely useful in elucidating the distribution and interaction of oxygen in the microstructure of sintered AlN ceramics, which has been heretofore an extremely difficult problem in microstructural and microchemical analysis of such sintered ceramics.

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