_{1}

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We studied the electrical characteristics of Al/methylene-blue/n-Si/Au Schottky diodes such as current-voltage, conductance-capacitance-voltage, and conductance-capacitance-frequency. We plotted rectification ratio vs. voltage (RR-V) of the diode. From I-V plots of the diodes, saturation current (
*I*
_{o}), and ideality factor (
*n*) were calculated. Barrier height (eΦ
_{B}) and series resistance (
*R*
_{S}) were calculated with Norde functions. The results show that in the Al/methylene-blue/n-Si/Au diode, the methylene-blue layer has a significant impact on electrical properties such as series resistance, barrier height, ideality factor, conductance, rectification ratio, and capacitance.

It is well known that Schottky diodes with organic components have many advantages over inorganic semiconductors in electronic devices such as easy fabrication, low cost, and applicability to rigid-flexible substrates [

Previous studies have examined Schottky barrier diodes with different organic components. Kılıçoğlu et al. studied Al/methyl-red/p-Si Schottky diodes. The structure demonstrated rectifying behavior [

Previous studies examined methyl-red and methylene-blue with p-Si Schottky barrier diodes [

We used n-Si wafers with (100) orientation, 250 µm thickness, and ρ = 10 Ω∙cm resistivity. The sample was chemically cleaned of chemical and organic contamination [_{4}H + H_{2}O_{2} + 6H_{2}O) and then in (HCl + H_{2}O_{2} + 6H_{2}O). Afterward, they were etched in HF:H_{2}O (1:10) for 30 seconds and rinsed in demonized water with ultrasonic vibration [

The ohmic contact on the back surface of the n-type Silisium (n-Si) wafer piece was fabricated by evaporating previously-cleaned Au [_{2}) atmosphere [^{−2} mol L^{−1} in methanol [^{−6} torr pressure on the front side to form a rectifying contact. The result was an Al/methylene-blue/n-Si/Au (Al/MB/n-Si) Schottky diode.

We plotted I-V measurements, from the I-V plot ideality factor (n) and saturation current (I_{o}) were calculated [_{S}) and barrier height (eF_{B}) were calculated [

G/w-C-V Measurements were performed at room temperature (300˚K) at 0.5 MHz frequency and G/w-C?f measurements at room temperature (300˚K) at 250 mV bias. We plotted G/w-C-V, C^{−2}-V and G/w-C-f measurements of the diode (

When there is an insulating layer between metal-semiconductor interfaces of a metal-semiconductor device, the current-voltage (I-V), according to thermionic emission theory for non-ideal condition, can be given as follows [

where n is ideality factor, V is forward bias voltage, e is the electron charge, R_{s} is series resistance, k is the Boltzmann constant, T is temperature in Kelvin, and I_{o} is the saturation current derived from the straight line intercept of the I axis at V = 0 and given by

In Equation (2), ^{2}×K^{2} for n-type Si) [_{B} is the effective barrier height.

The ideality factor n is determined from slope of the linear region of the forward bias in I-V from the ratio [

_{B}) of the Schottky diode obtained as 0.83 eV. High values of the ideality factor and barrier height imply that methylene-blue layer, native oxide layer, and contamination occurred at the metal-semiconductor interface [

To obtain series resistance (R_{s}) and barrier height (eΦ_{B}), Norde functions were used [

I(V) is the current obtained from I-V measurements, _{B}) determined using the minimum value of F(V)-V plot by means of the relationship

In Equation (5), F(V_{0}) is the minimum F(V) value and V_{0} is the voltage. The F(V)-V curves of the samples are shown in _{s}) of the diodes can be expressed as

where I_{min} is the current value at V_{0} [_{s}) and barrier height (eΦ_{B}) were obtained using Equations (5) and (6). From Norde’s functions, the series resistances (R_{s}) and the barrier heights (eΦ_{B}) of the Schottky diode obtained as 437 Ω and 0.89 eV respectively.

The barrier height and ideality factor of the diode were calculated as 0.83 eV and 2.8 using Equations (2) and (3) from the y-axis intercept and the linear slope of lnI - V, respectively. The ideality factor is greater than unity and shows deviation from an ideal diode. The deviation can be attributed to several effects such as the effect of organic layer, native oxide layer, contamination, and non-homogeneous interfacial (methylene) layer [

We measured the rectification ratio (RR) of Al/MB/n-Si Schottky diode. RR is calculated from the ratio of forward and reverse current at a certain bias using equation ^{5} at +2 V, which is lower than MS diodes and can be attributed to the methylene layer [

G/w-V and C-V measurements of diodes were carried out at 0.5 MHz, at room temperature, and in darkness (^{−2}-V was plotted for 0.5 MHz and reverse bias (_{0}) was obtained from the intercept of C^{−2}-V with the horizontal axis. Ideality factor (n = 3.1) and barrier height (eФ_{B} = 0.83 eV)_{ }can seen in the C^{−2}-V graph [

G/w-V, G/w-f and C-f measurements of diodes were carried out at 250 mV at room temperature, and in darkness (

The purpose of this paper was to explain the electrical properties of an Al/methylene-blue/n-Si/Au diode. The results show that the methylene-blue layer has a significant effect on electrical properties such as series resistance,

barrier height, ideality factor, interface state density, and capacitance of the diodes. The values of barrier height (0.83 eV), ideality factor (2.8), and series resistance (437 Ω) were found to be higher than a typical MS. High values imply that the methylene-blue layer, native oxide layer, and contamination occurred at the metal-semi- conductor interface.

When we analyze characteristics of G/w-V and C-V of diodes, the conductance and capacitance with negative voltage remain small, but with positive voltage peaks of conductance and capacitance occur.

The rectification ratio of the Al/methylene-blue/n-Si/Au was plotted as RR-V. The diode’s RR was about 10^{5} at +2 V, which was lower than that of other MS diodes and could be attributed to methylene blue layer.

The capacitance-frequency shows excess capacitance at low frequencies. We infer that interface states can follow a signal at low frequencies.

B.Bati, (2016) The Electrical Properties of Al/Methylene-Blue/n-Si/Au Schottky Diodes. Journal of Modern Physics,07,1-6. doi: 10.4236/jmp.2016.71001