Electrical Characteristics of an Ag/n-InP Schottky Diode Based on Temperature-Dependent Current–Voltage and Capacitance–Voltage Measurements

Abstract

The rectifying junction properties of an Ag/n-InP Schottky diode are investigated in a wide temperature range from 10 K to 300 K (−263 °C to 27 °C). The electronic structure of the junction is analyzed by the techniques of current–voltage I–V and capacitance–voltage C–V measurement as a function of temperature. The electrical parameters are characterized with the standard thermionic emission theory. The main electrical characteristics including the values of apparent barrier height $\phi_{\text{e}}$ and ideality factor n are found to be 0.414 eV and 1.008 at 300 K (27 °C), respectively, even though the value of barrier height $\phi_{\text{b}}$ at 300 K (27 °C) from C–V data is 0.417 eV. The $\phi_{\text{e}}$, n, and Richardson plot demonstrate strong temperature dependency; that is, the $\phi_{\text{e}}$ decreases, n increases, and the Richardson plot deviates with decreasing temperature. Such behaviors are attributed to Schottky barrier anomalies, which are explained by assuming the existence of a Gaussian distribution of nanometer-sized patches with low barrier height at the interface. The accurate theoretical models such as Tung’s lateral inhomogeneity and multi-Gaussian distribution to comment the barrier inhomogeneity on the electron transport across the interface are applied, and the comparisons between these approaches for the present experimental results are carried out. According to the multi-Gaussian distribution approach, the double-Gaussian nature of Ag/n-InP/In is commented by the values of the weighting coefficients, standard deviations, and mean barrier height calculated for each distribution. The total effective area of the patches $NA_{\text{e}}$ is calculated for high and low temperatures, and as a result, it is found that the low barrier regions influence significantly the electron transport at the interface of the junction. The discrepancy between I–V and C–V barrier heights is discussed based on a Gaussian approach. From the linear relationship between $\phi_{\text{e}}$ and n, the homogeneous barrier height $\phi_{\text{b}}$ is noted to be 0.418 eV. The values of $A^{*}$ (effective Richardson constant) and $\phi_{\text{b}}$ are determined from classic modified Richardson plot as $A^{*}$: 8.08 A cm⁻² K⁻² and $\bar{\phi }_{\text{b}}$: 0.416 eV and from Tung’s model as $A^{*}$: 9.35 A cm⁻² K⁻² and $\mathop {\phi_{\text{b}} }\limits^{\_}$: 0.418 eV, which demonstrates an excellent agreement with the theoretical value (9.4 A cm⁻² K⁻²) of n-InP. As a result, in order to obtain the more reliable values of $A^{*}$ and $\mathop {\phi_{\text{b}} }\limits^{\_}$, it could be reported that Tung’s lateral inhomogeneity approach is more meaningful; taking into account the effective patch area, which is significantly lower than the whole geometric area of the diode.