Antonella Sciuto

High responsivity 4H-SiC Schottky UV photodiodes based on the pinch-off surface effect

In this letter, high responsivity 4H-SiC vertical Schottky UV photodiodes based on the pinch-off surface effect, obtained by means of self-aligned Ni2Si interdigit contacts, are demonstrated. The diode area was 1mm2, with a 37% directly exposed to the radiation. The dark current was about 200pA at −50V. Under a 256nm UV illumination, a current increase of more than two orders of magnitude is observed, resulting in a 78% internal quantum efficiency. The vertical photodiodes showed an ultraviolet-visible rejection ratio >7×103 and a responsivity a factor of about 1.8 higher than a conventional planar metal-semiconductor-metal structure.

Highly Efficient Low Reverse Biased 4H-SiC Schottky Photodiodes for UV-Light Detection

Ultraviolet light detection has a wide range of scientific and industrial applications. In particular, SiC photodiodes have been proposed because of their robustness even in harsh environments, high quantum efficiency but excellent visible blindness, very low dark current, and high speed. Here, we report on the electrical and optical performances of high efficient large area 4 H-SiC Schottky photodiodes working in the photovoltaic regime. We demonstrate that the high signal-to-noise ratio along with the low operating reverse voltage in spite of the large sensitive area makes them suitable in low power consumption applications requiring high sensitivity down to 250 nm.

Design, fabrication, and testing of an integrated Si-based light modulator

We have fabricated and characterized a novel Si-based light modulator working at the standard communication wavelength of 1.5 /spl mu/m. It consists of a three-terminal bipolar mode field effect transistor integrated with a silicon rib waveguide on epitaxial Si wafers. The modulator optical channel is embodied within its vertical electrical channel. Light modulation is achieved moving a plasma of carriers inside and outside the optical channel by properly biasing the control electrode. The carriers produce an increase of the Si absorption coefficient. The devices have been fabricated using clean-room processing. Detailed electrical characterization and device simulations confirm that strong conductivity modulation and plasma formation in the channel are achieved. The plasma distribution in the device under different bias conditions has been directly derived from emission microscopy analyses. The device performances in terms of modulation depth will be presented.

Electro-optical response of ion-irradiated 4H-SiC Schottky ultraviolet photodetectors

Visible blind 4H-SiC UV detectors were investigated with respect to radiation hardness since they can find applications in the aerospace field. Effects of ion irradiation on their response were studied by monitoring the spectral response as a function of irradiation beam energy and dose. The devices irradiated by 1, 4, and 10MeV Si+-ion beam show a change of the response depending on the ion irradiation energy. The unexpected huge optical effect, compared to the negligible influence on reverse bias leakage current, was correlated to the nature of irradiation induced damage and to its location inside the optical active device layer.

Miniaturizable Si-based electro-optical modulator working at 1.5 μm

Optoelectronic devices are considered the innovative element for the next generation of microelectronic integrated circuits. For this purpose, both active and passive devices—extremely miniaturized—must be implemented. We fabricated and electro-optical Si-based light intensity modulator working at 1.5 μm using a bipolar mode field-effect transistor integrated within a Si rib waveguide. The principle of operation is the light absorption by a plasma of free carriers that can be opportunely moved inside or outside of the device optical channel by properly changing the control bias. The devices, only 100 μm long, were fabricated using epitaxial Si wafers and standard clean room processing. The optical characterization at 1.48 μm in static conditions shows a modulation of ∼90% while the dynamic electrical characterization provides a switching time of ≈10ns (foreseen modulation frequency of hundreds of MHz). A modulation depth above 25% is observed for modulation frequency up to 300 kHz.

Thin Metal Film Ni 2 Si/4H—SiC Vertical Schottky Photodiodes

Photodetection in the ultraviolet (UV) region has drawn extensive attention owing to its various applications in industrial, environmental, and even biological fields. In this letter, we report on the morphological and electro-optical characteristics of continuous thin metal film Ni2Si/4H-SiC photodiodes properly designed for the realization of an extremely compact digital sensor suited to measure the total sun UV radiation for environmental UV light monitoring.

Luminescence properties of SiOxNy irradiated by IR laser 808 nm: The role of Si quantum dots and Si chemical environment

We investigated optical, structural, and chemical properties of SiOxNy layers irradiated by CW IR laser during a time lapse of few milliseconds. We observed tunable photoluminescence signal at room temperature in the range 750–950 nm, without Si/SiO2 phase separation, depending on the IR laser power irradiation. Furthermore, no photoluminescence signal was recorded when the IR laser power density was high enough to promote phase separation forming Si quantum dots. By chemical analysis the source of the luminescence signal has been identified in a change of silicon chemical environment induced by IR laser annealing inside the amorphous matrix.

Temperature and Light Induced Effects on the Capacitance of 4H-SiC Schottky Photodiodes

The capacitance plays a key role in determining the timing performances of a detector. To date, this parameter has never been fully investigated in the study of SiC photodiodes electro-optical characteristics. In this paper, we report on the capacitance dependence of interdigitated 4H-SiC Schottky photodiodes on different operating parameters like reverse bias, temperature, light irradiance and illumination wavelength.

On the Aging Effects of 4H-SiC Schottky Photodiodes Under High Intensity Mercury Lamp Irradiation

Ultraviolet (UV) germicidal irradiation uses high-power 254-nm radiation from low-pressure mercury discharge lamps to kill or inactivate viral, bacterial, and fungal species. Since UV germicidal irradiation effectiveness depends primarily on the UV dose delivered to the microorganisms, it is essential to monitor the power emitted from the source by using appropriate UV-light detectors. We report on preliminary aging tests performed on high signal-to-noise ratio 4H-SiC Schottky photodiodes under high intensity mercury lamp irradiation (10 mW/cm2).

4H-SiC Schottky photodiodes for ultraviolet light detection

In recent years Silicon Carbide (SiC) photodiodes have been proposed for ultraviolet (UV) light detection because of their robustness even in harsh environments, high quantum efficiency in all the UV range (200 nm–400 nm), excellent visible blindness, low dark current and high speed. Here, we report on the electro-optical performances and use in application of high signal-to noise ratio low reverse biased 4H-SiC vertical Schottky photodiodes based on the pinch-off surface effect, obtained by means of self-aligned Nickel Silicide (Ni2Si) interdigitated contacts. The characteristics of these devices could make their use appealing also in nuclear applications like for example scintillation light detection.