Si photodiode

All S FG spectra were obtained by averaging 50 400 pulses per data point and were normalized against the intensity of the visible and infrared inputs, which were simultaneously monitored by a power meter (Oriel instruments. Model 70833 and 70811) and Si photodiode, respectively. 

Special UV-enhanced Si photodiodes can be made by positioning the p-n junction close to the surface. Then, quantum efficiencies of 50% can be achieved for A... 

Visible- or solar-blind UV sensors can be made from a Si photodiode by additionally using an optical filter that transmits UV radiation only, see below. A more detailed explanation of the physics of UV photodiodes (made from Si as well as from other semiconductor materials) can be found in Ref. [1]. 

The most convincing argument for using Si photodiodes in UV detection is the availability of strong expertise in electronic Si devices. Processing and performance of opto-electronic Si devices have been optimized for decades, and the UV-enhanced photodiode is a high-performance niche product that can be produced at a reasonable price, thanks to these efforts. Its probably most serious drawback is the necessity of using filters for visible-blind applications, which considerably increases the cost of sensors and reduces their otherwise optimum sensitivity. 

Very promising indeed is the ternary compound AlGaN. By shifting the Al/Ga ratio its spectral sensitivity can be tailored. The cut-off wavelength can be shifted between 380 nm and 310 nm [3]. Quantum efficiencies up to 50% have been obtained for SiC as well as for GaN, which is similar to the UV sensitivity of UV-en-hanced Si photodiodes. 

A popular UV sensor designed for flame monitoring is the SFH 530 sensor by Infinion. It is a UV-enhanced Si photodiode with optical filter, concentrator lens and operational amplifier in a TO-39 package. Flame-sensing in gas ovens is another potential application of the described technique. 

Another problem is degradation of the sensor due to the high UV dose. The radiation resistance of most photodiodes decreases with wavelengths. UV-enhanced Si photodiodes show a loss of 10% in sensitivity already after an accumulated dose of some hundred J/cm2 at X = 254 nm. This is the dose a sensor will have received over the lifetime of an Hg lamp. Special silicon nitride-protected photodiodes are stable up to 105 J/cm2. A filter combined with an attenuator may help to achieve the required selectivity and reduce the exposure of the detector. However, the radiation stability of the filter has to be guaranteed. 

Integrated fluorescent detection was also achieved by fabricating the interference filter and Si photodiode on a Si substrate on which a parylene channel was built [691]. 

Integrated fluorescence detection was also achieved using hydrogenated amorphous silicon PIN photodiodes fabricated on a glass chip [690], In another report, the integrated Si photodiode was used for fluorescent detection of DNA, with a LOD of 0.9 ng/pL [693],... 

Kamei, T., Paegel, B.M., Scherer, J.R., Skefley, A.M., Street, R.A., Mathies, R.A., Integrated hydrogenated amorphous SI photodiode detector for microfluidic bio-analytical devices. Anal. Chem. 2003, 75, 5300-5305. 

Fig. 5.2. I-V characteristics of (a) an illuminated Si photodiode [120] and (b) of an ITO/Cgo MEH-PPV/Ca solar cell [121]. Curve numbers and corresponding values of the concentration ratio R of fullerene MEH-PPV are given in figure (b). (c) Dark (curve 1) and illuminated (curve 2) I-V characteristics of an ITO/C6o PS Ooct-OPV5/Al device with an active area of 0.24 cm2 [127], Note the difference in the electric field dependence of the illuminated reverse bias current of the organic and Si diodes.

PROBLEM 10.5.7. What area of Si photodiodes is needed to supply 20 kWh of electrical power per day, if the solar radiance is O.lWcm-2 and the photoelectric efficiency is 14% ("Typical US household" need). 

PROBLEM 10.5.9. If a one-story house has 4000 ft of living space, and its flat roof is covered by the best crystalline Si photodiode solar collector, operating at 25% efficiency, and if the solar radiance is 0.1 W cm 2, estimate the power generated. 

An ultrafast time-resolved near- and mid-IR absorption spectrometer was designed to achieve high sensitivity, ultrafast time resolution, and broad tunability in the near- and mid-IR regions (see Fig. 2). The details of this spectrometer are described elsewhere (9). Briefly, MbCO was photolyzed with a linearly polarized laser pulse, whose polarization direction was controlled electronically by a liquid crystal polarization rotator. The photolyzed sample was probed with an optically delayed, linearly polarized IR pulse whose transmitted intensity was spectrally resolved with a monochromator and detected with either a Si photodiode (near-IR RilO cm-1 bandpass) or a liquid nitrogen-cooled InSb photodetector (mid-IR 3 cm-1 bandpass). To measure the sample transmission, this signal was divided by a corresponding signal from a reference IR pulse... 

State-of-the art Cree Research, Inc. UV SiC photodiodes are more sensitive than commercial Si photodiodes. The reverse dark current at room temperature in these devices is less than 1 pAcm 2 and a few nAcm 2 at 400 °C. 

In the typical PL-detected magnetic resonance experiment, the sample is excited by a laser or an intense lamp, and the intensity of the total PL or a PL band, dispersed by a monochromator, is monitored with a Si photodiode or a thermoelectrically cooled photomultiplier tube. The sample is concomitantly subjected to a slowly swept dc magnetic field and the microwave field chopped at v, . Microwave-induced changes A/ in the total PL intensity I or intensity of an emission band at the field-for-resonance are then detected by the lock-in amplifier. The amplitude A/// of the ODMR signal... 

Fig. 7.43 Sensitivity of a Si photodiode vs. wavelength and average laser power for 2 mA peak current and 1 ns width at 80 MHz repetition rate...

Si photodiodes have a poor sensitivity in the UV range. UV-enhanced Si PIN photodiodes are available, but usually do not perform well at short pulses. In fre-... 

The PD, e.g., a photomultiplier tube or a Si photodiode, can be placed in front of the sensing film ( front detection ) or behind the OLED array ( back detection ). The basic structure of the integrated OLED/sensor him in the back-detection geometry is shown in Fig. 3.2. In this configuration, the PD collects the PL that passes through the gaps between the OLED pixels. The... 

Fig. 3.7. Schematic of the structurally integrated OLED-based oxygen sensor (not to scale). The photodetector, a PMT or Si photodiode, is behind the OLED pixel array. The Ti02 nanoparticles, which are embedded in the dye PS-sensing film, act as a scattering medium, increasing the absorption of the EL by the dye...

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