Photodiodes quantum efficiency

We are here attempting to distinguish between two distinct types of event with different pulse shape characteristics. The first is a scintillation event in the CsI(Tl) crystal, for which a typical yield wiU give 52,000 optical photons per MeV energy deposit. When combined with the light collection and photodiode quantum efficiencies, this gives an overall conversion efficiency (OCE) of - 40 electrons/keV. The temporal decay of light from Csl... 

HgCdTe photodiode performance for the most part depends on high quantum efficiency and low dark current density (83,84) as expressed by equations 23 and 25. Typical values of at 77 K ate shown as a function of cutoff wavelength in Figure 16 (70). HgCdTe diodes sensitive out to a wavelength of 10.5 p.m have shown ideal diffusion current limitation down to 50 K. Values of have exceeded 1 x 10 . Spectral sensitivities for... 

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... 

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 p-type electrode is in depletion if a cathodic bias is applied. Illumination generates one electron per absorbed photon, which is collected by the SCR and transferred to the electrolyte. It requires two electrons to form one hydrogen molecule. If the photocurrent at this electrode is compared to that obtained by a silicon photodiode of the same size the quantum efficiencies are observed to be the same for the solid-state contact and the electrolyte contact, as shown in Fig. 4.13. If losses by reflection or recombination in the bulk are neglected the quantum efficiency of the electrode is 1. 

The SPAD detector is similar in design to other photodiodes except the electric field of its junction is better separated than in other photodiodes. This design better endures the flow of the avalanche current triggered by a photogenerated carrier and provides better performance than normal SSPD. SPAD have detection limits several orders of magnitude lower than conventional PMTs.(35) In addition, they have been shown to have higher quantum efficiency (QE) values than PMTs in the NIR region.(57)... 

The speed of response of the photodiode depends on the diffusion of carriers, the capacitance of the depletion layer, and the thickness of the depletion layer. The forward bias itself increases the width of the depletion layer thus reducing the capacitance. Nevertheless, some design compromises are always required between quantum efficiency and speed of response. The quantum efficiency of a photodiode is determined largely by the absorption coefficient of the absorbing semiconductor layer. Ideally all absorption should occur in the depletion region. This can be achieved by increasing the thickness of the depletion layer, but then the response time increases accordingly. 

A photodiode is illuminated with a green beam (532 nm) whose power is unknown. The photodiode is operating in the photovoltaic regime at room temperature. After illumination, the voltage induced in the photodiode is 34 mV. Calculate the incident power if the quantum efficiency is 0.65 and if the electrical current generated in the photodiode in the absence of illumination is 1 mA. 

Calculate the current induced in a photodiode with an inhinsic quantum efficiency of 0.90 when it is illuminated at room temperature with a 0.35 mW light beam whose wavelength is 1140 nm. The photodiode is working in the photoconductor regime, and in the absence of illumination no electrical current is generated by this photodiode. What happens if the photodiode is cooled down to 5 °C ... 

Figure 4. Spectral response and relative quantum efficiency of the 256 EC/17 linear photodiode array (4)...

Fig. 7. Energy spectrum of 662 keV photons detected in Csl at 77 K from the 137Cs (3 emitter (left) showing the photo peak and the Compton plateau. The low energy peak is due to photons back-scattered from the container. A similar spectrum is obtained for 1275 keV photons from the 22Na 0+ emitter (middle). In this case one also observes the 511 keV line from positron annihilation and its corresponding Compton plateau. The resolution is better than 6 % at 511 keV. The right spectrum shows the response of the photodiode to 22 and 88 keV X-rays from 109Cd. A Csl light yield of 26,000 photons/MeV at 511 keV is derived from this spectrum, assuming about 6000 electron-hole pairs for 22 keV X-rays. This is however a lower limit, as it assumes 100 % quantum efficiency for the photodiode...

Internal and External Quantum Efficiencies of Organic Photodiodes... 

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