Shota Izumi

Characterization of near-infrared n-type β-FeSi2/p-type Si heterojunction photodiodes at room temperature

n-type β-FeSi2/p-type Si heterojunctions were fabricated from β-FeSi2 films epitaxially grown on Si(111) by facing-target direct-current sputtering. Sharp film-substrate interfaces were confirmed by scanning electron microscopy. The current-voltage and photoresponse characteristics were measured at room temperature. They exhibited good rectifying properties and a change of approximately one order of magnitude in the current at a bias voltage of −1 V under illumination by a 6 mW, 1.31 μm laser. The estimated detectivity was 1.5×109 cm √Hz W at 1.31 μm. The results suggest that the β-FeSi2/Si heterojunctions can be used as near-infrared photodetectors that are compatible with silicon integrated circuits.

n-type β-FeSi2/intrinsic-Si/p-type Si heterojunction photodiodes for near-infrared light detection at room temperature

n-Type β-FeSi2/intrinsic-Si/p-type Si heterojunctions, prepared by facing-targets direct-current sputtering, were evaluated as near-infrared photodetectors. The built-in potential was estimated to be approximately 1 V from capacitance-voltage characteristics. Diodes with a junction area of 0.03 mm2 exhibited a junction capacitance of 4.4 pF at zero bias. At room temperature, the devices exhibited responsivity of 140 mA/W and external quantum efficiency of 13% at a bias voltage of −5 V. The detectivity at zero bias was estimated to be 2.8×109 cm√Hz/W at the wavelength of 1.31 μm. These results indicate their high application potential as near-infrared photodiodes integrated with Si.

Near-infrared photodetection of β-FeSi2/Si heterojunction photodiodes at low temperatures

n-type β-FeSi2/p-type Si heterojunction photodiodes were fabricated by facing-targets direct-current sputtering, and their near-infrared photodetection properties were studied in the temperature range of 50–300 K. At 300 K, devices biased at −5 V exhibited a current responsivity of 16.6 mA/W. The measured specific detectivity was remarkably improved from 3.5 × 109 to 1.4 × 1011 cmHz1/2/W as the devices were cooled from 300 K down to 50 K. This improvement is mainly attributable to distinguished suppression in heterojunction leakage current at low temperatures. The obtained results indicate that β-FeSi2/Si heterojunctions offer high potential to be employed as near-infrared photodetectors that are compatible with the current Si technology.

Near-Infrared Photodetection of n-Type β-FeSi2/Intrinsic Si/p-Type Si Heterojunctions at Low Temperatures

n-Type β-FeSi2/intrinsic Si/p-type Si heterojunction photodiodes were fabricated by facing-targets direct-current sputtering, and their infrared photodetection properties were studied at low temperatures. The rectification current ratio at bias voltages of ±1 V and the ratio of the photocurrent to the dark leakage current were dramatically enhanced with a decrease in temperature. The specific detectivities at 300 and 50 K were estimated to be 3.8×109 and 8.9×1011 cm Hz1/2 W-1, respectively. The enhanced detectivity upon cooling is attributed to the marked reduction in the dark leakage current. The insertion of the thin intrinsic Si layer slightly contributed to the suppression of the leakage current and the detectivity improvement. It was demonstrated that β-FeSi2 is a potential material for Si-compatible near-infrared photodetectors.

Fabrication of n-type β-FeSi 2 /p-type Si heterojunctions by pulsed laser deposition and their application to NIR photodiodes

n-Type β-FeSi2 thin films were fabricated on p-type Si(111) substrates by pulsed laser deposition (PLD) at a substrate temperature of 600 °C. The epitaxial relationships between the film and substrate were investigated by X-ray diffraction (XRD). Two types of epitaxial relationships co-existed in the film. The n-type β-FeSi2/p-type Si heterojunction showed a typical rectifying action in the dark and it exhibited a weak response for 1.31-μm irradiation at room temperature.