Advanced Micro Foundry announces the availability of its 1550-nm wavelength LIDAR sensor based on Germanium-on-Silicon Avalanche Photodetector Arrays (APD) technology. The company claims its LIDAR sensor offers superior performance and cost advantage over conventional solid-state sensors. Reportedly, the latter are fabricated with expensive materials, and encounter short range problem due to low power constraint on short wavelength 905 nm.
Over the past two decades, high-gain, low noise Si APDs and Silicon photomultipliers (SiPM) have been developed and commercialized for visible wavelength ranges. However, collimated laser beams of 905 nm and shorter wavelength are dangerous to pedestrians even at relatively low power, as the lens focuses the light onto a tiny spot on the retina and poses potential ocular hazards.
According to Advanced Micro Foundry (AMF), the safety requirements in aspect of maximum permissible exposure (MPE) thus limits the detecting range of LIDAR at these wavelengths with confined transmitter energy. In contrast, at 1550 nm, most of the light will be absorbed by the transparent parts of the eyeball before it reaches the retina, which relaxes the MPE requirement for near-infrared (NIR) LIDAR. The large MPE capability attracts industries’ attention of LIDAR at 1550nm, and its receiving component of APDs.
The state-of-the-art commercially available APDs at 1550 nm are mostly III-V APDs, which is non-CMOS compatible and high cost. AMF has reported a 310-GHz gain-bandwidth product SACM Ge APD back in 2013. However, in LIDAR applications, the receivers only detect the weak scattered light from the targets, which requires APDs with both high-sensitivity and large detection-area, to enhance the possibility of capturing the scattered light with better signal-to-noise ratio.
Recently, AMF developed such Ge-on-Si avalanche photodetector (APD) arrays working at 1550 nm that target LIDAR applications. Its single APD pixel reveals a responsivity of 3.2A/W at the normal operation voltage of 90% breakdown voltage, with a dark current of 2.2 mA, a breakdown thermal coefficient of 0.029 V/°C, and a 3-dB bandwidth of 9 GHz. The 25 pixels on a 5 x 5 APD array shows high uniformity, with a responsivity variation of less than 5%, with the bandwidth of up to 1GHz, which is suitable for Lidar application. For more info, visit Advanced Micro Foundry Pte. Ltd.