Abstract
and singly doped and codoped and single crystal fibers were grown using the laser heated pedestal growth method. Energy transfer from to was studied in these samples. No energy transfer between and was observed in codoped . This is because electrons excited into the states delocalize into the conduction band at a rate that is faster than the interionic energy transfer rate, whereas the converse is the case for doped with and . The energy transfer rate was determined to be on the order of . The transfer occurs before the excited electrons can be thermally promoted into the conduction band. From these results, it can be inferred that the thermal ionization rate from the lowest excited state at is less than at room temperature, whereas the delocalization rate into the conduction band is faster than this rate. The location of the and states relative to the valence and conduction band of these two materials has been determined through photoconductivity measurements.
- Received 17 October 2003
DOI:https://doi.org/10.1103/PhysRevB.69.235113
©2004 American Physical Society