A. Türüt

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.

Current-voltage and capacitance-voltage characteristics of Sn/rhodamine-101/n-Si and Sn/rhodamine-101/p-Si Schottky barrier diodes

The nonpolymeric organic compound rhodamine-101 (Rh101) film on a n-type Si or p-type Si substrate has been formed by means of the evaporation process and the Sn/rhodamine-101/Si contacts have been fabricated. The Sn∕Rh101∕n-Si and Sn∕Rh101∕p-Si contacts have rectifying contact behavior with the barrier height (BH) values of 0.714 and 0.827eV, and with ideality factor values of 2.720 and 2.783 obtained from their forward bias current-voltage (I-V) characteristics at room temperature, respectively. It has been seen that the BH value of 0.827eV obtained for the Sn∕Rh101∕p-Si contact is significantly larger than BH values of the conventional Sn∕p-Si Schottky diodes and metal/interfacial layer/Si contacts. Thus, modification of the interfacial potential barrier for metal/Si diodes has been achieved using a thin interlayer of the Rh101 organic semiconductor; this has been ascribed to the fact that the Rh101 interlayer increases the effective barrier height by influencing the space charge region of Si.The nonpolymeric organic compound rhodamine-101 (Rh101) film on a n-type Si or p-type Si substrate has been formed by means of the evaporation process and the Sn/rhodamine-101/Si contacts have been fabricated. The Sn∕Rh101∕n-Si and Sn∕Rh101∕p-Si contacts have rectifying contact behavior with the barrier height (BH) values of 0.714 and 0.827eV, and with ideality factor values of 2.720 and 2.783 obtained from their forward bias current-voltage (I-V) characteristics at room temperature, respectively. It has been seen that the BH value of 0.827eV obtained for the Sn∕Rh101∕p-Si contact is significantly larger than BH values of the conventional Sn∕p-Si Schottky diodes and metal/interfacial layer/Si contacts. Thus, modification of the interfacial potential barrier for metal/Si diodes has been achieved using a thin interlayer of the Rh101 organic semiconductor; this has been ascribed to the fact that the Rh101 interlayer increases the effective barrier height by influencing the space charge region of Si.

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.

The double Gaussian distribution of barrier heights in Au/n-GaAs schottky diodes from I-V-T characteristics

The current?voltage (I?V) and capacitance?voltage (C?V) characteristics of Au/n-GaAs contacts have been measured in the temperature range of 80?300 K. An abnormal decrease in the experimental BH ?b and an increase in the ideality factor n with a decrease in temperature have been observed. This behaviour has been attributed to the barrier inhomogeneities by assuming a Gaussian distribution of barrier heights at the metal?semiconductor interface. The temperature-dependent I?V characteristics of the Au/n-GaAs contact have shown a double Gaussian distribution giving mean barrier heights of 0.967 and 0.710 eV and standard deviations of 0.105 and 0.071 V, respectively. A modified ln(I0/T2) ? q2?2s/2k2T2 versus 1/T plot for the two temperature regions then gives and A* as 0.976 and 0.703 eV, and 13.376 and 8.110 A cm?2 K?2, respectively. Furthermore, a value of ?0.674 meV K?1 for the temperature coefficient has been obtained, and the value of ?0.674 meV K?1 for the Au/n-GaAs Schottky diode is in close agreement with those in the literature.

Effect of series resistance on the forward current-voltage characteristics of Schottky diodes in the presence of interfacial layer

Abstract In order to make an accurate determination of Schottky diode parameters such as the ideality factor, the barrier height and the series resistance [using forward current-voltage ( I - V ) characteristics in the presence of an interfacial layer], a novel calculation method has been developed by taking into account the applied voltage drop across the interfacial layer ( V i ). The parameters obtained by accounting for the voltage drop V i have been compared with those obtained without considering the above voltage drop. To examine the consistency of this approach, the comparison has been made by means of Schottky diodes fabricated on a n -type semiconductor substrate with different bulk thickness. It is shown that the voltage drop across the interfacial layer will increase the ideality factor and the voltage dependence of the I - V characteristics. In addition, it is shown that the series resistance value increases as the semiconductor bulk thickness has been increased.

Semiconductive polymer‐based Schottky diode

Polythiophene is easily obtained electrochemically on a Au surface in an acetonitrile/0.25 M LiClO4 solution. On the basis of this knowledge, we prepared a metal‐semiconductor‐metal Schottky diode, in which Au and Al were used as metals and freshly prepared polythiophene as a semiconductor. Current‐voltage and capacity‐voltage characteristics of this diode have been obtained under atmospheric conditions.

Determination of the density of Si-metal interface states and excess capacitance caused by them

Abstract Schottky diodes were fabricated by evaporation of Al on a strongly etched n-type Si surface for 3 min after mechanical cleaning. The measurements of one of the better working of the Al-nSi diodes has been carried out at room temperature. Two expressions were found for the ideality factor n by supposing that all the interface states at first are in equilibrium with the metal and then with the semiconductor. The diode showed non-ideal I–V behaviour with an ideality factor of 1.46. The density distribution of interface states was obtained from the forward bias I–V characteristics. Non-linearity or curvature in the reverse bias C -2 − V plots was a quantity called the “excess capacitance” C 0 caused by the presence of the interface states. The excess capacitance was observed to decrease with increasing frequency: this behaviour was ascribed to the fact that the apparent density of the interface states decreases with increasing frequency. In addition, the parameters obtained from C − V characteristics were corrected by means of a simple graphical method for excess capacitance suggested by Vasudev et al. and of a theoretical model of an MIS structure introduced by Fonash.

On temperature-dependent experimental I-V and C-V data of Ni/n-GaN Schottky contacts

We report the current-voltage (I-V) and capacitance-voltage characteristics (C-V) of Ni/n-GaN Schottky diodes. Gallium nitride is a highly promising wide band gap semiconductor for applications in high power electronic and optoelectronic devices which require Schottky barriers for modulating the channel mobile charge. The I-V and C-V characteristics of the diodes have been measured in the temperature range of 80–400 K with steps of 20 K. Thermal carrier concentration and barrier height versus temperature plots have been obtained from the C−2-V characteristics, and a value of α=−1.40 meV/K for temperature coefficient of the barrier height. The modified activation energy plot according to the barrier inhomogeneity model has given the Richardson constant A∗ as 80 or 85 A/(cm2 K2).