Samples were reactively etched using SF6 and Ar plasmas. The Ar-etched specimens exhibited a striking transition from a predominant blue luminescence band to a predominant yellow band after less than 300s of low-power illumination. It was concluded that the observation of metastable defects which were associated with both the yellow and blue bands had important implications for the explanation of defect-related luminescence in this material.

Reactive-Ion Etched Gallium Nitride: Metastable Defects and Yellow Luminescence. S.A.Brown, R.J.Reeves, C.S.Haase, R.Cheung, C.Kirchner, M.Kamp: Applied Physics Letters, 1999, 75[21], 3285-7