Electrical conduction in cubic GaN films grown on GaAs(001) by RF-MBE

The electrical conduction property of c-GaN films grown on GaAs(001) by RF-MBE has been studied in relation with the amount of the hexagonal phase inclusion, or cubic phase purity. In a high-phase-purity (93 %) film, the electron concentration and mobility at 300 K are typically 8×10 ¹⁷ cm^-3 and 110 cm²/V-s, respectively. It is known that a parallel conduction is occurring in which the high mobility region somewhat away from the hetero-interface dominates the conduction at higher currents. In a lower-phase-purity (75%) film, it is indicated that the low mobility region extends over the larger region of the film. Above the cubic phase purity of about 90%, the electron concentration rapidly decreases and the mobility rapidly increases by one or two orders of magnitudes, suggesting that the stacking faults are the major source of the carrier electrons and causing the scattering centers responsible for the low mobility region.