Electrical characteristics of Au/Ti/n-GaAs contacts over a wide measurement temperature range

We have fabricated Au/Ti/n-GaAs/In Schottky barrier diodes using the magnetron dc sputter technique. The capacitance–temperature (C–T) measurements with bias voltage as a parameter and the current–voltage (I–V) and capacitance–voltage (C–V) measurements have been made in the temperature range of 60–300 K. The temperature-dependent capacitance measurements have been made at 1.0 MHz. The capacitance versus temperature curve at each bias voltage has four regions with slopes different from each other. The capacitance decreases with a decrease in temperature at each bias voltage. Such a temperature-dependent behavior could be attributed to modulation of the space charge region caused by the emission of deep-level impurities or interface states. The carrier concentration calculated in the −1.0 to −2.0 V range of C−2 –V plots was close to the value of 7.43 × 1015 cm−3 given by the manufacturer around room temperature. The ideality factor value from the I–V characteristics has remained almost unchanged between 1.07 and 1.10 in the temperature range of 150–300 K, indicating that the current across the device obeys the thermionic emission current model quite well over the whole bias range at temperatures above 150 K. Therefore, the conventional Richardson plot in this temperature range has given a Richardson constant of 8.21 A (cm K)−2 , within experimental error, which is in very close agreement with the theoretical value of 8.16 A (cm K)−2 for n-type GaAs. Again, it has been seen that the ideality factor with the values of 1.10 at 150 K and 1.22 at 60 K does not show a considerable decrease. The experimental parameters show that the Au(90 nm)/Ti(10 nm)/nGaAs contact is a good candidate for electronic device applications.