Effect of Atomic Layer Deposited HfO2 thin Film Interfacial Layer on the Electrical Properties of Au/Ti/n-GaAs Schottky Diode

The electrical properties of Au/Ti/HfO2/n-GaAs metal/insulating layer/semiconductor (MIS) contact structures were analyzed in detail by the help of capacitance-voltage (C-V) and conductance-voltage (G-V) measurements in the temperature range of 60–320 K. The HfO2 thin film layer was obtained by atomic layer deposition technique (ALD). The main electrical parameters such as ideality factor (n) and barrier height (ΦB0) were determined for Au/Ti/n-GaAs and Au/Ti/HfO2/n-GaAs diodes using current-voltage (I-V) measurement at 300 K. The values of these parameters are 1.07 and 0.77 eV for the reference (Au/Ti/n-GaAs) diode, and 1.30 and 0.94 eV for the Au/Ti/HfO2/n-GaAs MIS diode, respectively. An interfacial charge density value of Qss= 4.14x1012 Ccm− 2 for the MIS diode was calculated from the barrier height difference of ΔΦ=0.94-0.77=0.17 V. Depending on these results, the temperature dependent C-V and G-V plots of the device were also investigated. The series resistance (Rs), phase angle, the interface state density (Dit), the real impedance (Z') and imaginary impedance (Z'') were evaluated using admittance measurements. The C and G values increased, whereas (Z'') and Z decreased with increasing voltage at each temperature. An intersection point being independent of temperature in the G–V curves appeared at forward bias side (≈1.4 V), after this intersection point of the G–V plot, the G values decreased with increasing temperature at a given voltage. The intersection points in total (Z) versus V curves appeared at forward bias side (≈1.7 V). The Nyquist spectra was recorded for the MIS structure showing single semicircular arcs with different diameters depending on temperature.