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APD

UV avalanche photodiodes (APD)

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SG02-APD-D5
UV Avalanche Photodiodes (SiC), 100 A/W maximum responsivitySingle Price: 100€Product Description
- SiC based avalanche photodiode (APD)
- broadband UVA+UVB+UVC, PTB reported high chip stability
- active area A = 0.20 mm²
- TO5 hermetically sealed metal housing, two isolated pins, one additional grounded pin
- max. responsivity is 100 A/W

UV Photodiodes FAQ

Why are there photodiodes with different chip active areas?

Summary:
Decreasing irradiance requires increasing chip active area. If the irradiance to be measured is unknown, an L-chip photodiode should be used for prototypes.
Detailed answer:
The active area of the chip determines how many photons can be collected by a photodetector. Semiconductor detectors, such as SiC UV photodiodes, convert photons into an electrical current, the photocurrent I. This photocurrent increases linearly with the irradiance and the active area of the chip. Since the price of the detector increases with the active area, the choice of area is essentially a compromise between cost and photocurrent. If you know the minimum and maximum irradiance you wish to measure with the UV photodiode, the following simplified formula gives a rough estimate of the photocurrent I for a given chip active area AChip. I=Achip *Eλ *1000 where I is the photocurrent in nA, A is the active chip area in mm² (enter values of 0.06 or 0.2 or 0.5 or 1 or 1.82 or 7.6 or 36) and Eλ is the spectral irradiance of the UV light source you like to measure in mW/cm². The minimum current (photodiode output at the lowest irradiance to be measured) should not be less than 500pA. If you do not know Eλ, the L-chip (1.00mm²) type photodiode should be used for a first evaluation step.

When do I need a broadband photodiode and when do I need filtered photodiodes for UVA, UVB, UVC or UV index?

Summary:
For UV measurement, unfiltered broadband SiC is used by default
Detailed answer:
By default, unfiltered broadband SiC is used for UV measurements. If a UV source also emits radiation that must not contribute to the sensor’s signal (e.g. UV medium pressure lamps used for water or air purification that also emit non-germicidal UV radiation), a filtered SiC detector (UVC, UVB+C or UVA only) should be selected.

Which photodiode do I use for 185nm and 172nm?

Summary:
Our SiC-VUV photodiodes are used here.
Detailed answer:
Our standard SiC photodiodes only have a low sensitivity below 220nm. Below approx. 200nm they have they no longer have any sensitivity. For applications where radiation below 220nm needs to be measured, our VUV (“vaccum UV”) photodiodes are used. Typical applications are the destruction (cracking) of organic carbons in fat or in water (TOC) at 185nm or the matting of paints at 172nm. VUV photodiodes are also used to monitor PFAS photolysis.

Do you produce SMD type photodiodes?

Summary:
Yes, but we do not recommend their use.
Detailed answer:
Yes, we manufacture 3535 SMD type photodiodes (ceramic package), but we recommend the use of metal TO photodiodes. The packaging and hermetic sealing of photodiode chips in metal TO housings with a fused glass window is a mature and extremely reliable process that has been in use for more than 50 years. A TO-packaged sglux SiC UV photodiode is usually the most reliable and durable component in a product, even when exposed to very high UV radiation or operated at high temperature levels. However, recent progress in the development of long life UV LEDs, also in the UVC range, allow UV low pressure tubes to be replaced by these LEDs, resulting in a significant potential reduction in product dimensions. The miniaturization of products such as UV transmittance measurement modules or point-of-use LED UVC disinfection modules allows our customers to move into new areas of application. Sometimes our TO-packaged UV photodiodes are considered too bulky. Our SiC SMD photodiode range is designed for these applications. The package consists of a ceramic body with a mineral window glass to make these SMD photodiodes as reliable as possible. However, TO type photodiodes remain the best choice in terms of durability, reliability and price.

You produce photodiodes with 2 pins and with 3 pins. What is the third pin good for?

Summary:
By default, 2-pin photodiodes are used.
Detailed answer:
By default, 2-pin photodiodes are used. One pin is connected to the metal body of the photodiode and to the anode. The other pin is isolated and connected to the cathode. A 3-pin photodiode is characterized by two isolated pins (connected to the anode and cathode) and one pin connected to the metal case. The 3-pin photodiode is used if the photodiode package is in contact with metal components of the customer's product.

What is the response time of a SiC photodiode?

Summary:
The response time is about 190ps (FWHM).
Detailed answer:
At the Helmholtz-Zentrum Berlin, investigations were carried out on pulse excitation with 266 nm fs laser pulses. The response time of the measured SiC photodiodes is determined by a decay constant of 7 ns at 0 V BIAS voltage. At a maximum BIAS voltage of -160 V, this converges in an exponential relationship towards 3.5 ns. The rise time could not be measured precisely with the available setup, but is faster than 80 ps (sigma), i.e. approx. 190 ps (FWHM).

What about the saturation of the photodiodes?

Summary:
An S-chip type photodiode saturates at around 4.2 kW/cm². Such a high irradiance is very unusual.
Detailed answer:
The saturation current Isat of a photodiode is determined by its open circuit voltage VOC and its series resistance RS according to the formula: Isat = VOC / RS A typical value (SiC photodiode) for VOC is 2.0 V and for RS = 5 Ohm. This gives Isat = 2.0 V / 5 Ohm = 0.4 A = 400 mA. The saturation radiant intensity z is calculated using the formula below: z = Isat / (S * A) Where S is the sensitivity of a photodiode and A is the active area. A typical value for S is 0.16 A/W and A = 0.06 mm² (valid for SG01S). This gives: zsat = 0.4 A / (0.160 A/W * 6 * 10-8 m²) = approx. 42 MW/m² = 4.2 kW/cm². Such a high irradiance is very unusual. However, some laser measurement applications can reach such irradiance levels for short periods of time. This may affect the output current of the photodiode. Please contact us for further information.

Is the photodiode waterproof?

Summary:
Yes.
Detailed answer:
Yes, the photodiode is hermetically sealed and, accordingly, water pressure proof. However, the rear side contact pins must not get in contact with water our moisture. This will influence the photodiode’s output current.