We have examined the effects of thermal annealing on electrical properties in molecular beam epitaxy (MBE) grown n-type GaN films by using variable temperature Hall effect measurement. We have investigated both undoped and Si-doped samples, and have found that the electron mobility increases by thermal annealing along with an increase or decrease in the carrier concentration, which eventually leads to the decrease in resistivity. The observed changes in the mobility and the carrier concentration can be explained by the model whereby shallow donors and deep acceptors both are diminished by thermal annealing. Changes in donor and acceptor concentrations have been estimated based on Hall effect measurement data at low temperatures.
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