Ö. Güllü

The effect of Schottky metal thickness on barrier height inhomogeneity in identically prepared Au/n-GaAs Schottky diodes

We have studied identically prepared Au(5 nm)/n-GaAs (35 dots) and Au(65 nm)/n-GaAs (38 dots) Schottky barrier diodes (SBDs) on the same n-type GaAs single crystal. A GaAs wafer has been prepared by the usual chemical etching, and evaporation of the metal has been carried out in a conventional vacuum system. The effective Schottky barrier heights (SBHs) and ideality factors obtained from the current–voltage (I–V) characteristics have differed from diode to diode. The SBH for the Au(5 nm)/n-GaAs diodes have ranged from 0.839 to 0.943 eV and the ideality factor n from 1.011 to 1.150. The SBH for the Au(65 nm)/n-GaAs diodes have ranged from 0.828 to 0.848 eV and the ideality factor n from 1.026 to 1.069. Our aim is to find the laterally homogeneous SBH values of the SBDs depending on Schottky metal thickness. The lateral homogeneous SBH values of 0.940 eV for the Au(5 nm)/n-GaAs and 0.866 eV for the Au(65 nm)/n-GaAs diodes have been calculated from a linear relationship between barrier height (BH) and the ideality factor, which can be explained by lateral inhomogeneities of the SBH, respectively.

Electrical characterization of organic-on-inorganic semiconductor Schottky structures

We prepared a methyl red/p-InP organic–inorganic (OI) Schottky device formed by evaporation of an organic compound solution directly to a p-InP semiconductor wafer. The value of the optical band gap energy of the methyl red organic film on a glass substrate was obtained as 2.0 eV. It was seen that the Al/methyl red/p-InP contacts showed a good rectifying behavior. An ideality factor of 2.02 and a barrier height (Φb) of 1.11 eV for the Al/methyl red/p-InP contact were determined from the forward bias I–V characteristics. It was seen that the value of 1.11 eV obtained for Φb for the Al/methyl red/p-InP contact was significantly larger than the value of 0.83 eV for conventional Al/p-InP Schottky diodes. Modification of the interfacial potential barrier for the Al/p-InP diode was achieved using a thin interlayer of the methyl red organic semiconductor. This ascribed to the fact that the methyl red interlayer increases the effective Φb by influencing the space charge region of InP.

Fabrication and electrical properties of organic-on-inorganic Schottky devices

In this paper, we fabricated an Al/new fuchsin/p-Si organic?inorganic (OI) Schottky diode structure by direct evaporation of an organic compound solution on a p-Si semiconductor wafer. A direct optical band gap energy value of the new fuchsin organic film on a glass substrate was obtained as 1.95?eV. Current?voltage (I?V) and capacitance?voltage (C?V) measurements of the OI device were carried out at room temperature. From the I?V characteristics, it was seen that the Al/new fuchsin/p-Si contacts showed good rectifying behavior. An ideality factor value of 1.47 and a barrier height (BH) value of 0.75?eV for the Al/new fuchsin/p-Si contact were determined from the forward bias I?V characteristics. A barrier height value of 0.78?eV was obtained from the capacitance?voltage (C?V) characteristics. It has been seen that the BH value of 0.75?eV obtained for the Al/new fuchsin/p-Si contact is significantly larger than that of conventional Al/p-Si Schottky metal?semiconductor (MS) diodes. Thus, modification of the interfacial potential barrier for Al/p-Si diodes has been achieved using a thin interlayer of the new fuchsin organic semiconductor; this has been ascribed to the fact that the new fuchsin interlayer increases the effective barrier height because of the interface dipole induced by passivation of the organic layer.

Fabrication and electrical properties of Al/Safranin T/n-Si/AuSb structure

We have fabricated an Al/Safranin T (ST)/n-Si/AuSb device and have investigated its current?voltage (I?V), capacitance?voltage (C?V) and capacitance?frequency (C?f) characteristics at room temperature. The barrier height and ideality factor values of 0.78 eV and 3.52 have been obtained from the forward bias current?voltage plot. The value of the barrier height was compared with the barrier height value of 0.50 eV of a conventional Al/n-Si diode. This was attributed to the ST organic film modifying the effective barrier height by affecting the space charge region of the inorganic Si semiconductor substrate. A modified Nordes function combined with the conventional forward I?V method has been used to extract the parameters including barrier height and series resistance. The barrier height and series resistance obtained from Nordes function have been compared with those from Cheung functions, and it has been seen that there is a good agreement between the barrier height values from both methods. It has also been seen that the values of capacitance are almost independent of frequency up to a certain value of frequency, whereas at high frequencies the capacitance has decreased. The higher values of capacitance at low frequencies have been attributed to the excess capacitance resulting from the interface states in equilibrium with the n-Si that can follow the alternating current (ac) signal.

Temperature-dependent behavior of Ti/p-InP/ZnAu Schottky barrier diodes

The current–voltage (I–V) characteristics of Ti/p-InP Schottky diodes have been measured in a wide temperature range with a temperature step of 20 K. An experimental barrier height (BH) Φap value of about 0.85 eV was obtained for the Ti/p-InP Schottky diode at 300 K. A decrease in the experimental BH Φap and an increase in the ideality factor n with a decrease in temperature have been explained on the basis of a thermionic emission mechanism with the Gaussian distribution of the barrier heights due to the BH inhomogeneities at the metal–semiconductor interface. and A* as 1.01 eV, and 138 A cm−2 K2, respectively, have been calculated from a modified ln(I0/T2) − q2σ2s/2k2T2 versus 1/T plot. This BH value is in close agreement with the values of 0.99 eV obtained from the Φap versus 1/T and ln(I0/T2) versus 1/nT plots.

Gamma irradiation-induced changes at the electrical characteristics of organic-based Schottky structures

We have studied electrical parameters of an Al/methyl violet/p-Si Schottky device by using current–voltage and capacitance–voltage–frequency measurements under γ irradiation at room temperature. Experimental results have shown that γ radiation gives rise to an increase in the barrier height, the ideality factor and the interfacial state density, while the series resistance decreases by applied radiation.

Fabrication and electrical characterization of a silicon Schottky device based on organic material

An Al/methyl violet (MV)/n-Si/AuSb Schottky structure was fabricated and its current–voltage (I–V), capacitance–voltage (C–V) and capacitance–frequency (C–f) characteristics were investigated at room temperature. A modified Nordes function combined with conventional forward I–V method was used to extract the parameters including barrier height (BH) and series resistance. The BH and series resistance obtained from Nordes function have been compared with those from Cheung functions, and it was seen that there is good agreement between the BH values from both methods. It was also seen that the values of capacitance are almost independent of frequency up to a certain value of frequency, whereas at high frequencies the capacitance decreased. The higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the n-Si that can follow the alternating current (ac) signal.

Analysis of the series resistance and interface state densities in metal semiconductor structures

The electrical properties of Co/n-Si metal-semiconductor (MS) Schottky structure investigated at room temperature using current-voltage (I-V) characteristics. The characteristic parameters of the structure such as barrier height, ideality factor and series resistance have been determined from the I-V measurements. The values of barrier height obtained from Nordes function were compared with those from Cheung functions, and it was seen that there was a good agreement between barrier heights from both methods. The series resistance values calculated with Cheungs two methods were compared and seen that there was an agreement with each other. However, the values of series resistance obtained from Cheung functions and Nordes functions are not agreeing with each other. Because, Cheung functions are only applied to the non-linear region (high voltage region) of the forward bias I-V characteristics. Furthermore, the energy distribution of interface state density was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The results show that the presence of thin interfacial layer between the metal and semiconductor.