Necati Yalçin

Temperature dependent barrier characteristics of CrNiCo alloy Schottky contacts on n-type molecular-beam epitaxy GaAs

The current–voltage (I–V) characteristics of CrNiCo alloy Schottky contacts on a molecular-beam epitaxy n-GaAs substrate have been measured over the temperature range of 130–330 K and have been interpreted based on the assumption of a Gaussian distribution of barrier heights due to barrier height inhomogeneities that prevail at the interface. It is shown that the occurrence of Gaussian distribution of then barrier heights is responsible for the decrease of the apparent barrier height Φb0, increase of the ideality factor n and nonlinearity in the activation energy plot at low temperatures. A Φb0 vs 1/T plot was drawn to obtain evidence of a Gaussian distribution of the barrier heights, and values of Φb0(T=0)=1.02 eV and σ0=0.105 V for the mean barrier height and zero-bias standard deviation, respectively, have been obtained from this plot. Thus, a modified ln(I0/T2)−q2σ02/2k2T2 vs 1/T plot gives Φb0(T=0) and A* as 1.02 eV and 5.13 A/cm2 K2, respectively, without using the temperature coefficient of the b...

Interpreting the nonideal reverse bias C-V characteristics and importance of the dependence of Schottky barrier height on applied voltage

This work presents an attempt related to the charging behaviour of interface states to the nonideal forward bias current-voltage (I-V) and the reverse bias capacitance-voltage (C-V) characteristics of AlnSi Schottky barrier diodes. The diode showed nonideal I-V behaviour with an ideality factor of 1.50 and was thought to have a metal-interface layer-semiconductor configuration. Considering that the interface states localized at the interfacial layer-semiconductor interface are in equilibrium with the semiconductor, the energy distribution of the interface states was exactly determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height, θe. The determination of the intercept voltage and interface state density was made by means of a simple interface charge model which has been developed in detail. The I-V characteristics were used for determining the voltage dependence of the barrier height. Although the change in barrier height with applied biasis small, it is important for exactly determining the shape of the interface state density distribution curve. At a frequency of 500 kHz, the nonlinear reverse bias C−2−V plot with the curvature concave downward has been only thought of to be due to the contribution of the capacitance of the interface state charges. It is concluded that the nonlinear nature of C−2−V plots in the frequency range 50–200 kHz has been caused by the interface state charges as well as inversion layer and inversion layer charges. It has been understood by means of the interface state charge model that the C−2−V plots cannot only be interpreted in terms of the contribution of the interface state charges to the device capacitance.

Parameter extraction from non-ideal C−V characteristics of a Schottky diode with and without interfacial layer

Abstract In this study, we have attempted to interpret experimentally observed non-ideal AlpSi Schottky diode I-V and C−2−V characteristics which are due to an interface layer, interface states and fixed surface charge. A value of 0.68 eV for the barrier height qΦBo for AlpSi diodes without interface layer and fixed surface charge has been obtained from C−2−V characteristics and a value of 0.20 eV for the neutral level of the surface states has been found. Furthermore, the value of the barrier height qΦBp without fixed surface charge and the effective barrier height qΦBp,o are separately obtained from C−2-V characteristics. In addition, values of interface state density Dit have been calculated.

The bias-dependence change of barrier height of Schottky diodes under forward bias by including the series resistance effect

Schottky barrier height shifts depending on the interfacial layer as well as a change of the interface state charge with the forward bias while considering the presence of bulk (semiconductor) series resistance are discussed both theoretically and experimentally. It has been concluded that the barrier height shift or increase in Schottky diodes is mainly due to the potential change across the interfacial layer and the occupation of the interface states as a result of the applied forward voltage. One assumes that the barrier height is controlled by the density distribution of the interface states in equilibrium with the semiconductor and the applied voltage. In nonideal Schottky diodes, the values of the voltage drops across the interfacial layer, the depletion layer and the bulk resistance are given in terms of the bias dependent ideality factor, n, different from those in literature. These values are determined by a formula obtained for Vi and Vs by means of change of the interface charge with bias.

Space‐charge‐limited current effects in n‐type CuInSe2/Au Schottky diodes

Schottky diodes, fabricated by evaporating thin films of Au onto n‐type single crystals of CuInSe2 have been shown to exhibit space‐charge‐limited current effects under foward bias. The observed characteristics are associated with the presence of a high‐resistivity layer close to the metal contact.

Thermal stability of Cr-Ni-Co alloy Schottky contacts on MBE -GaAs

The thermal stability of the Schottky barrier height of Cr-Ni-Co alloy Schottky contacts on an MBE n-GaAs substrate has been investigated using current-voltage (I-V) and capacitance-voltage (-V) techniques after thermal annealing for 5 min in an atmosphere at several temperatures in the 200-C range. It has been found that the value of (0.83 or 0.84 eV) remains constant up to C in the forward I-V mode. Because of the presence of an interfacial layer between the alloy contact and GaAs, an ideality factor value of 1.31 was obtained for as-deposited samples. This value decreases to 1.18 with increasing annealing temperature up to C. At annealing temperatures above C, the ideality factor n starts to increase. This has been explained in terms of the presence of different metallic-like phases produced by chemical reactions between the alloy and GaAs because of the annealing process. The (C-V) values obtained from the reverse-bias -V curves of the as-deposited and annealed diodes at 1 MHz are in the range 0.96-1.09 eV. The difference (0.13-0.26 eV) between (C-V) and the (I-V) is in close agreement with values reported in literature.