Advanced numerical modeling of avalanche infrared photodetectors
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Abstract
Infrared detectors are critical for a variety of applications within the commercial, scientific, and defense communities. Applications such as commercial LiDAR systems or the James Webb Space Telescope rely on infrared detectors with high sensitivity and fast response times to achieve their missions. The avalanche photodiode is a class of detectors with high bandwidth and internal signal amplification which can improve the sensitivity of a detector by overcoming the noise associated with readout electronics.
The transport and multiplication properties of avalanche photodiodes are predicated on large electric fields in the device significantly shifting the distribution of the particles to higher energies, where the transport properties change. The modeling of these effects requires simulation tools which accurately incorporate the microscopic processes affecting the energy distribution within the device.
In this work, a general-purpose three-dimensional Monte Carlo simulation tool, FBMC3D, is developed and subsequently employed to study infrared avalanche photodiode detectors. The software can employ both analytic and numerically computed descriptions of the semiconductor band structure, and real space is discretized using an unstructured tetrahedral mesh suited to the description of modern semiconductor devices with irregular geometries, doping profiles, and compositional gradients. FBMC3D combines and extends the steady advancements of the Monte Carlo technique of the previous decades and allows for the simulation of devices on a scale that has traditionally been restricted to drift-diffusion packages.
This tool is then applied to the study of HgCdTe infrared avalanche photodetectors. Monte Carlo transport parameters are determined for a compositional range of HgCdTe corresponding to much of the infrared spectrum. The parameter model
is able to fit the multiplication properties of a number of devices of varying architectures and compositions in the range. Finally, the assembled transport models are used to design a long wavelength infrared avalanche photodiode with significantly improved performance with respect to what has been reported in literature.