The effect of 60Co (γ-ray) irradiation on the electrical characteristics of Au/SnO2/n-Si (MIS) structures

doi:10.1016/j.radphyschem.2007.02.006

Radiation Physics and Chemistry

Volume 77, Issue 1, January 2008, Pages 74-78

https://doi.org/10.1016/j.radphyschem.2007.02.006 Get rights and content

Abstract

The effect of ⁶⁰Co (γ-ray) irradiation on the electrical properties of Au/SnO₂/n-Si (MIS) structures has been investigated using the capacitance–voltage (C–V) and conductance–voltage (G/ω−V) measurements in the frequency range 1 kHz to 1 MHz at room temperature. The MIS structures were exposed to γ-rays at a dose rate of 2.12 kGy/h in water and the range of total dose was 0–500 kGy. It was found that the C–V and G/ω−V curves were strongly influenced with both frequency and the presence of the dominant radiation-induced defects, and the series resistance was increased with increasing dose. Also, the radiation-induced threshold voltage shift (ΔV_T) strongly depended on radiation dose and frequency, and the density of interface states N_ss by Hill–Coleman method decreases with increasing radiation dose.

Introduction

MIS structures consist of semiconductor substrate covered by an insulator layer upon which a metal electrode is deposited. The presence of insulating interface layer makes them rather sensitive to irradiation. It is known that energetic ⁶⁰Co γ-ray irradiation can generate electronic surface states at the semiconductor–insulator (such as Si–SnO₂ or Si–SiO₂) interface in MIS structures. Exposure of the MIS structures to γ-rays will cause, by means of the Compton electrons, electron–hole pair generation and changes in the crystal lattice (Chin and Ma, 1983; Ma, 1975; Feteha et al., 2002). When the MIS structures are stressed with an external bias, these electron–hole pairs would be separated by the strong local internal electric field at grain boundaries. Electrons are swept out of the insulator layer quickly by the electric field while the holes slowly and could be trapped by the defects. Recently, the radiation response of MIS devices has been found to change significantly when these devices are exposed to irradiation stress treatments (Nicollian and Goetzberger, 1965; Zainninger and Holmes-Siedle, 1967; Winokur et al., 1976; Benedetto and Boesch, 1984; Winokur et al., 1984; Da Silva et al., 1987; Schwank et al., 1986; Ma, 1989; Witczak et al., 1992; Candelori et al., 1999; Tataroğlu et al., 2003).

Da Silva et al. (1987) were among the first to make a systematic observation of the after-irradiation behavior of radiation-induced interface states (N_ss) in MIS devices.

When localized interface states exist at the semiconductor–insulator interface, the device behavior is different from an ideal case. The reason is mainly due to the interruption of the periodic lattice structure at the surface (Nicollian and Goetzberger, 1965; Tataroğlu et al., 2003), surface preparation, and formation of insulator layer and impurity concentration of semiconductor (Hung and Cheng, 1987). This interface states usually cause a bias shift and frequency dispersion in the capacitance–voltage (C–V) and conductance–voltage (G/ω−V) curves (Ma, 1975). To determine the interface state density traps, various measurement techniques such as the high-low frequency capacitance (Castagne and Vapaille, 1971; Kelberlau and Kassing, 1979), quasi-static capacitance (Kuhn, 1970), surface admittance (Kar and Varma, 1985) and conductance techniques have been developed, and among them the more important ones are high–low frequency capacitance and conductance technique (Hung and Cheng, 1987).

The promising physical properties of SnO₂ thin film and their superior chemical stability have motivated its application in many devices, such as solar cells, gas sensors, catalyses devices, and transparent conducting electrodes (Moreno et al., 1997; Dazhi et al., 1994; Chrisey and Hubler, 1994; Auciello and Engemann, 1993). Even though a lot of works have been done on SnO₂ thin films, to the best of knowledge, the effect of radiation on SnO₂ thin films has not been studied.

In this work, we present the effect of ⁶⁰Co γ-ray irradiation on the electrical characteristics of MIS structures using capacitance–voltage (C–V) and conductance–voltage (G–V) measurements.

Section snippets

Experimental details

The metal–insulator–semiconductor (Au/SnO₂/n-Si) structures used in this work were fabricated using n-type (P-doped) single crystals silicon wafer with 〈1 1 1〉 surface orientation, 280 μm thick, 2″ diameter and 4.45 Ω cm resistivity. The Si wafer was degreased for 5 min in boiling trichloroethylene, acetone and ethanol consecutively and then etched in: first H₂SO₄, H₂O₂ and 20% HF solution, then 6HNO₃:1HF:35H₂O and 20% HF solution. Preceding each cleaning step, the wafer was rinsed thoroughly in

Frequency-dependent C–V and G/ω−V measurements

Although the frequency and irradiated characteristics of one of the diodes, MIS1, was presented in this work, other devices fabricated under the same condition showed almost the same characteristics with very similar diode parameters. Fig. 1(a) and (b) shows the measured capacitance–voltage (C–V) and conductance–voltage (G/ω−V) characteristics of Au/SnO₂/n-Si (MIS1) structure for different frequencies, respectively. Both the C–V and G/ω−V characteristics show frequency dispersion. In the

Conclusion

The effect of frequency and γ-ray irradiation on the electrical characteristics of Au/SnO₂/n-Si Schottky diode has been studied using C–V and G/ω−V measurements. Experimental results show that the capacitance (C) and conductance (G/ω) decrease with increasing frequency due to a continuous distribution of N_ss in equilibrium with Si. The series resistance gives two peaks in the shape of a hump at about zero bias, decreasing and disappearing with increasing frequencies. But, above 2.5 V, it begins

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The effect of 60Co (γ-ray) irradiation on the electrical characteristics of Au/SnO2/n-Si (MIS) structures

Abstract

Introduction

Section snippets

Experimental details

Frequency-dependent C–V and G/ω−V measurements

Conclusion

J. Non-Cryst. Solids

Surf. Sci.

Microelectron. J.

Renewable Energy

Solid-State Electron.

Sol. Energy Mater. Sol. Cells

Solid-State Electron.

Solid-State Electron.

Microelectron. J.

Solid-State Electron.

Characterization of interface states at Au/InSb/InP (100) Schottky barrier diodes as a function of frequency

Vacuum

Multicomponent and Multilayered Thin Films for Advanced Microtechnologies: Techniques Fundamentals and Devices

MOSFET and MOS capacitor responses to ionizing radiation

IEEE Trans. Electron. Nucl. Sci.

Gate-width dependence of radiation-induced interface traps in metal/SiO2/Si devices

Appl. Phys. Lett.

Pulsed Laser Deposition of Thin Films

The effect of ⁶⁰Co (γ-ray) irradiation on the electrical characteristics of Au/SnO₂/n-Si (MIS) structures

Gate-width dependence of radiation-induced interface traps in metal/SiO₂/Si devices