Search
Menu
CASTECH INC - New Building the Bridge of Light

Novel Photodiode Cuts Excess Noise, Enhances Detection Efficiency

Facebook X LinkedIn Email
Researchers at the University of Sheffield designed and developed an avalanche photodiode (APD) with significant potential for low photon detection. The highly sensitive gallium arsenide antimonide/aluminum gallium arsenide antimonide (GaAsSb/AlGaAsSb) separate absorption and multiplication avalanche photodiode (SAM-APD), which the researchers believe signifies a milestone in the development of infrared (IR) APDs, demonstrates very little added noise to interfere with signal recognition.

The novel APD features a GaAsSb absorption region and an AlGaAsSb avalanche region. It features low tunneling current in addition to high usable avalanche gain and extremely low excess noise factors.

APDs are widely used in optical receivers for high-speed, optical fiber-based communication and lidar applications, which require extremely sensitive photodiodes that are capable of detecting very low levels of light intensity — in some cases, detection down to a few photons or single-photon level.

When operated in the Geiger mode, APDs can be used in single-photon detection, such as quantum key distribution and quantum imaging. The signal-to-noise ratio (SNR) in an APD-preamplifier module can be enhanced by the internal avalanche gain of APDs if the dominant noise source is the preamplifier. A significant increase in SNR, relative to pin photodiodes, can be achieved if the randomness in the impact ionization process is small. APDs typically have a higher SNR than pin photodiodes because APDs apply reverse voltage, which causes them to experience internal gain.

To build the APD, the researchers combined a semiconductor alloy with a wider bandgap semiconductor. The semiconductor alloy is based on a GaAsSb absorption region that has excellent detection efficiency at IR wavelengths up to 1700 nm.
Researcher Tarick Blain and team members designed an extremely low excess noise avalanche photodiode with a GaAsSb absorption region and an AlGaAsSb avalanche region. Core applications for the APD include lidar and optical communications. Courtesy of the University of Sheffield.
Researcher Tarick Blain and team members designed an extremely low excess noise avalanche photodiode with a GaAsSb absorption region and an AlGaAsSb avalanche region. Core applications for the APD include lidar and optical communications. Courtesy of the University of Sheffield.
The low-noise APD incorporates an appropriate doping profile to suppress tunneling current from the absorption region. It achieves an avalanche gain of about 130 at −49.6 V at room temperature, and it exhibits low excess noise factors of 1.52 and 2.48 at the gain of 10 and 20, respectively.

Gentec Electro-Optics Inc   - Measure Your Laser MR

At the gain of 20, the measured excess noise factor of 2.48 is more than 3× lower than a commercial indium gallium arsenide/indium phosphide (InGaAs/InP) SAM-APD.

“One of the long-standing limitations of infrared APDs is a relatively high added noise from the multiplication process that limits the maximum multiplication factor,” said professor Chee Hing Tan. “This, in turn, prevented infrared APDs from reaching the performance limit predicted by established models.

“Our breakthrough result, with an excess noise factor of 2.48, is approaching the theoretical lower limit of 2. This provides the pathway to realize extremely low-noise APD that I believe can generate step changes in optical communication and long-range lidar.”

The research was published in Applied Physics Letters (www.doi.org/10.1063/5.0139495).

Published: February 2023
Glossary
avalanche photodiode
A device that utilizes avalanche multiplication of photocurrent by means of hole-electrons created by absorbed photons. When the device's reverse-bias voltage nears breakdown level, the hole-electron pairs collide with ions to create additional hole-electron pairs, thus achieving a signal gain.
photodiode
A two-electrode, radiation-sensitive junction formed in a semiconductor material in which the reverse current varies with illumination. Photodiodes are used for the detection of optical power and for the conversion of optical power to electrical power. See avalanche photodiode; PIN photodiode.
optical communications
The transmission and reception of information by optical devices and sensors.
lidar
Lidar, short for light detection and ranging, is a remote sensing technology that uses laser light to measure distances and generate precise, three-dimensional information about the shape and characteristics of objects and surfaces. Lidar systems typically consist of a laser scanner, a GPS receiver, and an inertial measurement unit (IMU), all integrated into a single system. Here is how lidar works: Laser emission: A laser emits laser pulses, often in the form of rapid and repetitive laser...
OpticsSensors & Detectorsavalanche photodiodeavalanche photodetectorphotodiodeMaterialsAlGaAsGaAsSbResearch & TechnologyeducationUniversity of SheffieldEuropeoptical communicationsCommunicationslidarsingle photon detectionphoton detectionphoton detectorsTechnology News

We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.