FAQs | Si APDs

Can APDs be ranked by breakdown voltage?

The S12023-02/-05/-10/-10A, S12051, S12086, and S3884 near infrared type APDs (low bias voltage operation) are available as standard products in three ranks of 80 to 120 V, 120 to 160 V and 160 to 200 V.

Can APDs be ranked by breakdown voltage?

Linearity deteriorates from an output current of about several hundred microamperes.

What is the definition of the APD multiplication factor (gain)?

The APD gain is the ratio of the photocurrent multiplied by application of a high bias voltage to the photocurrent generated without multiplication with no bias voltage applied.

Why do low bias type and low temperature coefficient type of near infrared Si APDs have different lower limits of operating temperature?

Low bias operation type and low temperature coefficient type use the same package. However, since low bias operation type has a large temperature coefficient, its terminal capacitance becomes larger at low temperatures causing the response speed to drop, so the lower limit of the operating temperature is specified as -20 deg.C.

What is the difference between APDs and photomultiplier tubes?

APDs are semiconductor devices and have higher quantum efficiency compared to photomultiplier tubes. APDs can also be produced in small sizes, are unaffected by magnetic fields, and feature a wide dynamic range. However, APDs have disadvantages such as large noise and a low multiplication factor, so photomultiplier tubes are superior when detecting extremely low light levels.

How can I maintain a constant gain even if temperature varies?

Common techniques are to monitor the forward voltage at the PN junction or to use a thermistor in order to detect temperature fluctuations. Feedback is then applied to the APD bias voltage to maintain a constant gain. Another technique is to drive the APD at a constant current and make the bias voltage automatically follow up on temperature fluctuations.

What is the difference between Si APDs and PIN photodiodes?

The lower detection limit of PIN photodiodes is determined by load resistance thermal noise and amplifier noise. APDs have an internal gain effect that multiplies the signal to a level higher than the thermal noise, allowing high-speed and low-noise light detection.

Are APDs with a large photosensitive area available?

To fabricate a large area Si APD, processing techniques are needed for making the gain uniform over the entire photosensitive area. Currently, photosensitive areas up to 10 × 10 mm (S8664-1010) are available.

What types of APD array devices are available?

We handle custom orders for APD arrays requiring special photosensitive area sizes, contours, gain variations and gaps between elements, etc. As a standard product, we offer the S8550-02 (4 × 8 elements).

To what level can APDs detect faint light?

On the S2381 near infrared APD (low bias operation), a typical NEP (noise equivalent power) is approximately 5×10-16 W/Hz1/2.

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