Persistent photoconductivity and carrier transport in AlGaN/GaN heterostructures treated by fluorine plasma

Fluorine plasma treatment technique can effectively incorporate fluorine atoms into the AlGaN barrier, depleting the two-dimensional electron gases (2DEGs) in the channel of AlGaN/GaN high electron mobility transistors and converting the device from depletion mode to enhancement mode. To reveal the underlying physical mechanisms, temperature dependent persistent photoconductivity (PPC) and Hall measurements are conducted in AlGaN/GaN heterostructures treated by CF4 plasma. Weakly temperature dependent 2DEG mobility and much more pronounced PPC effect are observed in the F-treated sample. An energy barrier of 624 meV for electrons recaptured by the F-related centers is extracted from the PPC decay behaviors. (C) 2008 American Institute of Physics