Mixed Signal/Analog

Highly sensitive SPAD devices based on modular process technology

5th July 2019
Lanna Cooper

X-FAB Silicon Foundries continues to develop semiconductor solutions to address the most difficult of design challenges. It has now announced the availability of Avalanche Photodiode (APD) and Single-Photon Avalanche Diode (SPAD) products for implementation in scenarios where there are extremely low light conditions to contend with and augmented sensitivity is required, as well as tight timing resolutions involved.

Based on the company’s popular 180nm high voltage XH018 process, these function block devices deliver a combination of elevated performance parameters and straight forward integration.

The APD has a strong linear gain figure, and is fully scalable - going from just ten to several hundred micrometer dimensions. The proprietary X-FAB quenching circuit used in the SPAD results in a dead time of less than 15ns - thereby supporting high bandwidth.

In addition, its low dark count rate (<100 counts/s/µm²) means that it is far less susceptible to thermal noise. The high Photon Detection Probability (PDP) of the SPAD ensures that a much higher proportion of incident photons trigger an avalanche, and this is maintained across an extensive range of wavelengths (e.g. 40% at 400nm).

The X-FAB APD and SPAD can be utilised in a broad spectrum of different applications - including proximity sensing, LiDAR, Time of Flight (ToF), medical imaging (CT and PET) and scientific research. Being AEC-Q100 compliant, they are suitable for deployment within automotive systems.

Furthermore, the low breakdown voltage (less than 20V) that has been achieved facilitates their incorporation onto customer dies. As integral parts of the X-FAB design kit, they are fully characterised, and can easily be combined with other modules featured in the XH018 process. Models for optical and electrical simulation, along with a specific application note, will help designers to integrate these devices into their circuitry within a short time period.

As well as being supplied in a function block format, a quenching reference circuit that fully demonstrates the capabilities of the SPAD is also available.

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