Defect related persistent effects in MBE grown gallium nitride epilayers

The results of spectral as well as temperature dependent photoconductivity measurements performed on molecular beam epitaxy (MBE) grown gallium nitrid e (GaN) epilayers are reported in this work. It is observed that persistent photoconductivity (PPC) is seen in only those materials which contain the yellow luminescence (YL) band. It is further revealed that there exists a c lear threshold for the observation of PPC in our GaN epilayers both at 77 a nd 297 K. The relevance of this threshold with the YL band in GaN is discus sed within the scope of our experimental observations. (C) 1999 Elsevier Sc ience B.V. All rights reserved.