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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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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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