Low Temperature Thin-Film Silicon Diodes for Consumer Electronics

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 × 10⁴ A/cm ². We found that the use of microcrystalline silicon (μc-Si) i- and n-layers 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.