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Temperature dependent current-voltage characteristics of n-type nanocrystalline-FeSi2/p-type Si heterojunctions fabricated by pulsed laser deposition
(2014-01-08)
Promros, Nathaporn
;
Iwasaki, Ryuhei
;
Funasaki, Suguru
;
Yamashita, Kyohei
;
Li, Chen
n-Type NC-FeSi<inf>2</inf>/p-type Si heterojunctions were successfully fabricated by PLD, and their forward current-voltage characteristics were analyzed on the basis of thermionic emission theory (TE) in the temperature range from 300 down to 77 K. With a decrease in the temperature, the ideality factor was increased while the zero-bias barrier height was decreased. The calculated values of ideality factor and barrier height were 3.07 and 0.63 eV at 300 K and 10.75 and 0.23 eV at 77 K. The large value of ideality factor indicated that a tunneling process contributes to the carrier transport mechanisms in the NC-FeSi<inf>2</inf> films. The series resistance, which was estimated by Cheung's method, was strongly dependent on temperature. At 300 K, the value of series resistance was 12.44 Ω and it was dramatically enhanced to be 1.71× 105 Ω at 77 K. © (2014) Trans Tech Publications, Switzerland.
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Electrical characteristics of n-type nanocrystalline FeSi2/intrinsic Si/ p-type Si heterojunctions prepared by facing-targets direct-current sputtering
(2014-01-01)
Promros, Nathaporn
;
Funasaki, Suguru
;
Iwasaki, Ryuhei
;
Yoshitake, Tsuyoshi
n-Type nanocrystalline FeSi<inf>2</inf>/intrinsic Si/p-type Si heterojunctions were prepared by FTDCS. In order to estimate their diode parameters such as ideality factor, barrier height and series resistance, their current-voltage characteristics were measured in the temperature range from 300 to 77 K and analyzed on the basis of thermionic emission theory and Cheung's method. Based on thermionic emission theory, the ideality factor was calculated from the slope of the linear part from the forward lnJ-V characteristics. The barrier height was calculated once the saturation current density was derived from the straight line intercept of lnJ-V plot at a zero voltage. The obtained results exhibit an increase of ideality factor and a decrease of barrier height at low temperatures, which might be owing to inhomogeneity of material and non-uniformity of charge at the interface. Based on Cheung's method, the ideality factor and barrier height were estimated from y-axis intercept of dV/d(lnJ)-J plot and y-axis intercept of H(J)-J plot, respectively. The series resistance was analyzed from the slopes of dV/d(lnJ)-J and H(J)-J plots. The values of ideality factor and barrier height obtained from this method are in agreement with those obtained from the thermionic emission theory. The obtained series resistances from dV/d(lnJ)-J and H(J)-J plots, which were approximately equal to each others, were increased as the temperature decreased. This result should be owing to the increased ideality factor and remarkably reduced carrier concentrations at low temperatures. © (2014) Trans Tech Publications, Switzerland.
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Diode parameters of heterojunctions comprising p-type si substrate and n-type β-FeSi2 thin films
(2014-01-01)
Promros, Nathaporn
;
Funasaki, Suguru
;
Takahara, Motoki
;
Shaban, Mahmoud
;
Yoshitake, Tsuyoshi
N-Type β-FeSi<inf>2</inf>/p-type Si heterojunctions have been successfully fabricated by facingtargets direct-current sputtering at a substrate temperature of 600 °C without post-annealing and their current-voltage characteristics were measured at low temperatures ragne from 300 K down to 50 K. The ideality factor, saturation current and series resistance were estimated by the thermionic emission theory and Cheung’s method. By the thermionic emission theory, we calculated the ideality factor from the slope of the linear part from the forward lnJ-V and estimated the saturation current density from the straight line intercept of lnJ-V at a zero voltage. As decreasing temperatures from 300 down to 50 K, the value of ideality factor increased from 1.2 to 15.6, while the value of saturation current density decreased from 1.6 × 10-6 A/cm2 to 3.8 × 10-10 A/cm2. From the plots of dV/d(lnJ)-J and H(J)-J by Cheung’s method, the obtained values of series resistances are consistent with each other. The series resistances analyzed from both plots increased as decreasing temperatures.
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Fabrication of mesa structural n-type nanocrystalline-FeSi2/p-type Si heterojunction photodiodes by liftoff technique combined with photolithography
(2013-12-01)
Funasaki, Suguru
;
Promros, Nathaporn
;
Iwasaki, Ryuhei
;
Takahara, Motoki
;
Shaban, Mahmoud
Mesa structural n-type nanocrystalline (NC) FeSi<inf>2</inf>/p-type Si heterojunctions were fabricated by a liftoff technique combined with photolithography in order to improve the diode performance, particularly to reduce the parasitic capacitance. Their current-voltage characteristics were experimentally studied in the dark and under illumination using a 1.31 μm laser at room temperature. Their junction capacitance density and leakage current density were evidently reduced as compared with those of the normal structural diodes. The mesa diode exhibits a good rectifying action with a rectification ratio of approximately three orders of magnitude at bias voltages of ±1 V. The photodetection was clearly observed owing to the suppression in the dark current. The estimated detectivity is 2.0 × 109 cm√Hz/W at zero bias, which is an order of magnitude larger than that of the normal structural diodes. This should be because the formation of interface states is reduced accompanied by the interface area reduction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Current transport mechanism of n-type nanocrystalline FeSi2/intrinsic si/p-type si heterojunctions fabricated by facing-targets direct-current sputtering
(2013-10-29)
Promros, Nathaporn
;
Funasaki, Suguru
;
Iwasaki, Ryuhei
;
Yoshitake, Tsuyoshi
N-Type nanocrystalline FeSi<inf>2</inf>/intrinsic Si/p-type Si heterojunctions were successfully fabricated by FTDCS and their forward current-voltage characteristics at low temperatures were analyzed on the basis of thermionic emission theory. The analysis of J-V characteristics exhibits an increase in the ideality factor and a decrease in the barrier height at low temperatures. The values of ideality factor were estimated to be 2.26 at 300 K and 9.29 at 77 K. The temperature dependent ideality factor together with the constant value of parameter A indicated that a trap assisted multistep tunneling process is the dominant carrier transport mechanism in this heterojunction. At high voltages, the current transport mechanism is dominated by SCLC process. © (2013) Trans Tech Publications, Switzerland.
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Characterizations of mesa structural near-infrared n-type nanocrystalline-FeSi2/p-type si heterojunction photodiodes at low temperatures
(2013-10-04)
Promros, Nathaporn
;
Iwasaki, Ryuhei
;
Funasaki, Suguru
;
Yamashita, Kyohei
;
Yoshitake, Tsuyoshi
In order to reduce the parasitic capacitance, mesa structural n-type NC-FeSi<inf>2</inf>/p-type Si heterojunctions were fabricated by photolithography. Their current-voltage characteristics were measured in the dark and under illumination using a 1.31 μm laser in the temperature range of 60 - 300 K. Their junction capacitance density was evidently reduced as compared with that of the normal structural diodes. The dark current was markedly reduced with a decrease in the temperature. At 60 K, a rectifying current ratio in the dark became more than five orders of magnitude at ±1V. The ratio of the photocurrent to the dark current was dramatically enhanced to be approximately two orders of magnitude, and the detectivity was calculated to be 1.5 × 1011 cmHz1/2/W at -1V. The obtained results showed a remarkable improvement in the device performance as compared with those at 300 K. © (2013) Trans Tech Publications, Switzerland.

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