Temperature Dependence of Leakage Current in Segmented a-Si:H n-i-p Photodiodes
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0989-A19-04
Temperature Dependence of Leakage Current in Segmented a-Si:H n-i-p Photodiodes Jeff Hsin Chang1, Tsu Chiang Chuang1, Yuri Vygranenko1, Denis Striakhilev1, Kyung Ho Kim1, Arokia Nathan2, Gregory Heiler3, and Timothy Tredwell3 1 Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, N2L 3G1, Canada 2 London Centre for Nanotechnology, University College, London, WC1H OAH, United Kingdom 3 Eastman Kodak Company, Rochester, NY, 14652-3487 ABSTRACT Hydrogenated amorphous silicon (añSi:H) nñiñp photodiodes may be used as the pixel sensor element in large-area array imagers for medical diagnostics applications. The dark current level is an important parameter that dictates the performances of these types of pixelated imaging devices. Through measurements performed at different ambient temperatures, the leakage current components of segmented añSi:H nñiñp photodiodes were extracted and analyzed. It was found that the central component of the reverse current depends exponentially on bias and temperature. The activation energy of this component is independent of bias. The peripheral component of reverse current exhibits linear bias dependence at temperatures up to 50∞C, while the contribution of this component diminishes at high temperatures. The dependence of dark current components on bias and temperature could be described by compact analytical equations. The model of forward and reverse dark current characteristics in temperature range was implemented in Verilog-A hardware description language. INTRODUCTION Hydrogenated amorphous silicon (añSi:H) nñiñp photodiodes are commonly used in large area flat-panel imagers (FPI) for medical imaging applications [1]. The leakage current level of these devices has important implications as it dictates the performances of the imaging systems. While a major portion of the total leakage current in large añSi:H nñiñp photodiodes may be attributed to central leakage, the peripheral component, affected by the details of the sensor structure and fabrication process, may very well dominate the total leakage current level in small photodiodes, thereby limiting the practical dimensions of such devices. The majority of studies of the leakage components were performed at room temperature for various photodiode sizes, deposition temperature, and etching processes to separate the central and peripheral components [2, 3]. Even though temperature dependence of the reverse dark current (ID) for large area photodiodes were previously analyzed [4], the temperature dependences of various current components are still to be investigated. This work presents a systematic study of the temperature dependence of dark current characteristics for segmented añSi:H nñiñp photodiodes, allowing the separation of different leakage components at various temperatures.
EXPERIMENT Glass
Cr
a-Si:H
a-SiNx:H
ITO
Al
Fig. 1: Cross-sectional diagram of the fabricated añSi:H nñiñp photodiode.
Square segmented añSi:H n-i-p photodiodes of various sizes were prepar
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