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Why do electron traps at EC –0.6 eV have inverse correlation with carbon concentrations in n-type GaN layers?

We found that the graphite elements in a metalorganic vapor phase epitaxy reactor are a significant source of iron atoms, and lead to the formation of E3 electron traps at an energy EC –0.6 eV in n-type GaN layers. Thus, the previously reported inverse correlation between the E3 trap and carbon concentrations can be explained in terms of the correlation between the growth parameters. A high V/III ratio reduced carbon incorporation and simultaneously decreased the growth rate, resulting in increased iron incorporation in the layer grown. A high temperature also reduced carbon incorporation, while iron incorporation and the formation of E3 traps were both increased by enhanced etching of the graphite elements. By optimizing the growth conditions, we successfully suppressed both E3 trap formation and carbon incorporation in n-type GaN layers on 2 inch wafers.