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New Avalanche Photodiode IR Sensors Reported as 12X More Sensitive

January 31, 2024 by Aaron Carman

Designers can now see more with less light thanks to new optical sensors from a University of Sheffield spinout company.

Phlux Technology, a University of Sheffield spinout company, has announced its first product: the Noiseless InGaAs APD series of high-sensitivity, low-noise avalanche photodiodes (APDs). Current generations of photodiodes face noise and sensitivity limitations, especially in long-range sensing applications such as LiDAR. Phlux claims its new line of APDs could provide new performance gains for future generations of these sensor systems. The company says the product line is 12x more sensitive than traditional APDs.  

 

New avalanche photodiodes

New avalanche photodiodes allow designers to improve the sensitivity of IR detection systems, increasing the range and accuracy of many sensors.

 

This article takes a closer look at the three inaugural members of the Noiseless InGaAs series and gives readers the highlights of their performance metrics. We'll also discuss targeted applications to put in context how better sensitivity and noise performance could translate to longer-range sensors.

 

Photodiodes Vs. Avalanche Photodiodes

Photodiodes convert incident light energy in the form of photons into electrical energy. If an incident photon has sufficiently high energy, it can create a hole-electron pair that is separated by the built-in electric field of the diode. This movement of charges corresponds to an electrical current, which can be read to determine the power density of the light.

 

Avalanche photodiodes leverage an “avalanche layer”

Avalanche photodiodes leverage an “avalanche layer” to increase the number of excited charges, allowing for a hardware-enabled current gain to improve sensitivity. 
 

APDs, on the other hand, are built for high-sensitivity scenarios where very few photons make it back to the sensor. In this case, the device creates a higher current using an “avalanche effect,” where the accelerated charges create more charges, increasing the amount of current generated per photon. This avalanching can be electrically controlled and improves sensitivity with tradeoffs on noise performance.

 

New APDs Feature Ultra-Low Noise Performance

The Noiseless InGaAs series of APDs features low-noise factors, with values of 1.08 and 1.86 at avalanche gains of 10 and 40, respectively. This translates to a noise equivalent power of 5.2–5.6 fW/Hz, enabling small amounts of incident light to be detected. The noise performance is highly dependent on the configured avalanche gain, with very low noise at low gain and a greater noise factor at higher gain levels.

 

As avalanche gain increases, the noise performance can degrade

As avalanche gain increases, the noise performance can degrade. Compared to other technologies, however, the new APD shows improved noise performance even at high gains. 
 

In addition to noise performance, the avalanche gain of the system can be configured to over 120, giving designers more headroom on the signals they can detect. The new series also supports a wide spectrum, advertised as working from 900–1650 nm wavelengths (with the peak responsivity at ~1550 nm). The sensors operate from -40°C–85°C, and can support an input power of up to 0 dBm. The devices come with optical apertures of 30, 80, and 200 µm.

 

Versatile Light Detection

As optical measurements become increasingly important for applications such as autonomous driving, unique and versatile sensors could be critical in enabling the next generation of smart sensors.

The Noiseless InGaAs series can be used in various applications, including laser range finding, LiDAR, and optical time-domain reflectometry. In all cases, the improved sensitivity and noise performance of the Phlux APDs may enable longer ranges and more sensitive measurement equipment, respectively.

 


 

All images used courtesy of Phlux Technology.