Different optical absorption edges in AlN bulk crystals grown in m- and c-orientations

作者：Lu P^*; Collazo R; Dalmau R F; Durkaya G; Dietz N; Sitar Z

来源：Applied Physics Letters, 2008, 93(13): 131922.

DOI：10.1063/1.2996413

AlN single crystals were grown on m-plane (10 (1) over bar0) and c-plane (000 (1) over bar) AlN seeds under identical growth conditions. The m-plane AlN crystals exhibited substantially lower oxygen incorporation, similar to 10(18) cm(-3), than the c-plane crystals, similar to 10(19) cm(-3). By investigating optical transmission spectra, m-plane AlN had absorption bands at 4.05 and 4.35 eV, while c-plane AlN had an absorption band edge at 4.85 eV. These below bandgap absorption bands strongly correlate with the reported transitions related to Al vacancy-impurity complexes, such as the complex of an Al vacancy and two oxygen atoms, (V(Al)-2O(N))(1)-and the complex of an Al vacancy and one oxygen atom, (V(Al)-O(N))(2-), becoming the major cause for the poor, below bandgap optical transparency (alpha>200cm(-1)) of these crystals.

• 出版日期2008-9-29