Transition processes occurring under continuous and stepwise heating of GaAs surface-barrier structures

Evolution of the capacitance-voltage (C-U) and current-voltage (If-U and Ir-U) characteristics of solid metal-semiconductor structures (Ni/GaAs) in the process of their continuous and stepwise heating are studied. Properties of the initial structures obey the theory of thermionic emission. It has been shown that as a result of continuous heating, the rectifying structures become ohmic at a temperature of TOhm=720 K, which is substantially lower than the melting points of the metal or the metal-semiconductor eutectic. For comparison, properties of the structures annealed at different temperatures Tann are measured after cooling to room temperature (stepwise heating). In this case, I-U characteristics are closer to the initial ones for annealing temperatures Tann<T0=553 K; for Tann>T0, the characteristics display excess currents; and, finally, for Tann exceeding T0 by 200–300 K, the characteristics become purely ohmic. It is suggested that these effects are due to a chemical interaction between Ni and GaAs, which changes the properties of the semiconductor surface.