Temperature dependent I-V characteristics of an Au/n-GaAs Schottky diode analyzed using Tung's model

The current-voltage (I-V) characteristics of Au/n-GaAs contacts prepared with photolithography technique have been measured in the temperature range of 80-320 K. The ideality factor and barrier height (BH) values have remained almost unchanged between 1.04 and 1.10 and at a value of about 0.79 eV at temperatures above 200 K, respectively. Therefore, the ideality factor values near unity say that the experimental I-V data are almost independent of the sample temperature, that is, contacts have shown excellent Schottky diode behavior above 200 K. An abnormal decrease in the experimental BH Φb and an increase in the ideality factor with a decrease in temperature have been observed below 200 K. This behavior has been attributed to the barrier inhomogeneity by assuming a Gaussian distribution of nanometer-sized patches with low BH at the metal-semiconductor interface. The barrier inhomogeneity assumption is also confirmed by the linear relationship between the BH and the ideality factor. According to Tung's barrier inhomogeneity model, it has been seen that the value of σT=7.41×10−5 cm2/3 V1/3from ideality factor versus (kT)−1 curve is in close agreement with σT=7.95×10−5 cm2/3 V1/3 value from the Φeff versus (2kT)−1 curve in the range of 80-200 K. The modified Richardson ln(J0/T2)−(qσT)2(Vb/η)2/3/[2(kT)2] versus (kT)−1 plot, from Tung's Model, has given a Richardson constant value of 8.47 A cm−2 K−2which is in very close agreement with the known value of 8.16 A cm−2 K−2 for n-type GaAs; considering the effective patch area which is significantly lower than the entire geometric area of the Schottky contact, in temperature range of 80-200 K. Thus, it has been concluded that the use of Tung's lateral inhomogeneity model is more appropriate to interpret the temperature-dependent I-V characteristics in the Schottky contacts.