Barrier characteristics and interface properties of Au/Ti/n-InAlAs Schottky contacts

The InAlAs surface morphology (AFM), chemical composition (XPS) and the Ti/InAlAs interface structure (HREM), during the Au/Ti/n-In_0.52Al_0.48As/InP(001) mesa-structure Schottky barrier formation, were studied. The current-voltage (I-V) dependences analysis of the formed Schottky barrier in the temperature range of 100–380 K was carried out. It was shown that the I-V dependences are well described by the thermionic emission theory at temperatures above 200 K with the ideality factor and the barrier height close to 1.09 and 0.7 eV, respectively. At temperatures below 200 K, the I-V behavior is attributed to the Schottky barrier anomalies, which are explained by the existence of nanometer-sized patches with a low barrier height having a Gaussian distribution (Tung model). According to this model, the temperature dependences of the barrier height and ideality factor were described with the following parameters: the homogeneous barrier height of 0.88 eV and standard deviation of 10⁻⁴ cm^2/3V^1/3. In the analysis of the modified Richardson plot, the Richardson constant (10.7 Acm⁻² K⁻²) and the area fraction (24%), occupied by the patches with a low barrier height and diameter ~80 nm, were calculated. The patches appearance is explained by the presence of the spikes detected on the InAlAs surface by the AFM method.