The electrical characteristics and microstructures of n-type (100) GaAs bonded interfaces were systematically investigated. Experimental results indicated that GaAs did not bond directly to itself, but via an amorphous oxide layer at 400 °C. When temperatures increased above 400 °C, the oxide bonded area declined and finally disappeared. Electrical resistance decreased with bonding temperature. However, the resistance increased with temperatures exceeding 850 °C.