Effect of n-GaAs surface preparation and RF power on the electrical characteristics of W/n-GaAs Schottky diode fabricated by RF sputtering

Large area W/n-GaAs/In Schottky diodes A and B were fabricated by RF Sputter deposition of W using a rf power of 200 Watt for 45 min., on chemically etched and sputter etched polished surfaces of n-GaAs, respectively. The W/n-GaAs Schottky diode C was prepared by deposition of W on the chemically etched polished surface of n-GaAs by RF Sputtering using a rf power of 450 Watts for 20 min. The I-V, and 1 MHz C-V data for the diode A, indicated that W formed a good quality, stable rectifying contact to chemically etched n-GaAs surface, with a rectification ratio (r) of 300, ideality factor (n) of 1.39, reverse saturation current (I₀) of 1.2×10^-6 A and the C-V barrier height (φ_bo) of 1.5 V. However, the diodes B (with r=20, I₀=2.9×10^-5 A, n=1.43 and φ_bo=1.4 V) and C (with r=30, n=2.1, I₀= 2.6×10^-5 A, and φ_bo=1.2 V) showed poor rectification properties. The high values for the low frequency forward capacitance in the diodes B and C, indicated that the formation of high density surface defects during the RF sputter etching of the polished surface of n-GaAs, and by the sputter deposition of W on the chemically etched surface of n-GaAs, using high rf power, caused the degradation in the quality of the W/n-GaAs Schottky contacts