Low Temperature Thin-film Silicon Diodes for Consumer Electronics
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A15.5.1
Low Temperature Thin-film Silicon Diodes for Consumer Electronics Qi Wang, Scott Ward, Anna Duda, Jian Hua, Paul Stradins, Richard S. Crandall, Howard M. Branz, Frank Jeffrey1, Hao Lou2, Craig Perlov2, Warren Jackson2, Ping Mei2, and Carl Taussig2 Electronic Materials and Devices Division, National Renewable Energy Laboratory (NREL), 1617 Cole Blvd., Golden, CO 80401 USA Email: [email protected] 1 Iowa Thin Film Technologies (ITFT), AMES, IA, 50010 USA 2 Hewlett-Packard Laboratory, 1501 Page Mill Rd., Palo Alto, CA 94304 USA ABSTRACT We have developed high current density thin-film silicon n-i-p diodes for low cost and low temperature two-dimensional diode-logic memory array applications. The diodes are fabricated at temperatures below 250°C on glass, stainless steel, and plastic substrates using hot-wire chemical vapor deposition (CVD). The 0.01-mm2 standalone diodes have a forward current-density (J) of near 10 kA/cm2 and a rectification ratio over 107 at ±2 V. The 25 µm2 array diodes have J > 104 A/cm2 and rectification of 105 at ±2V. On plastic substrates, we have also used plasma-enhanced CVD to deposit 10-µm diameter diodes with J ~ 5 x 104 A/cm2. We found that the use of microcrystalline silicon (µc-Si) i- and nlayers results in higher current-density diodes than with amorphous silicon. Reducing the diode area increases the forward current density by lowering the voltage drop across the external series resistances. A prototype diode array memory based on 10-micron devices was successfully demonstrated by monolithically integrating diodes with a-Si:H switching elements. High current density diodes have potential applications in a variety of large area, thin-film electronic devices, in addition to a-Si:H-based memory. This could widen the application of thin-film silicon beyond its present industrial applications in thin-film transistors, solar cells, bolometers and photo-detectors.
INTRODUCTION Hydrogenated amorphous silicon (a-Si:H) diodes have been fabricated by many groups in the past. The diodes have good rectification ratio, but the forward current density is quite low, less than 50 A/cm2. [1-4] Many applications require a higher current density to drive an active element. For example, we are developing memory arrays based on devices that are each a series-connected combination of a high-current diode and an antifuse element. [5-7] The two-terminal diode addressed devices have advantages over the standard three-terminal transistors addressed devices. These advantages include simpler processing and a higher density of devices per unit area.[8] a
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A15.5.2
In this paper, we report our investigations leading to high-current-density thin-silicon diodes deposited at low temperature (< 250°C). [9] The low processing temperature permits deposition of these diodes on low-cost substrates such as glass, metal foil, or flexible plastics. Low-temperature and high-performance diodes are therefore critical to development of electronics based on two-terminal 2D arra
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