Many III-V digital alloy avalanche photodiodes have experimentally demonstrated very low excess noise. The presence of minigaps and enhanced valence band effective mass leads to the enhanced performance. Using first principle calculations and environment-dependent tight binding model we study the correlation of these properties with material parameters like stress. Furthermore, using NEGF formalism we study how these minigaps and mass enhancement impact the electron tunneling and phonon scattering processes in digital alloys. Based on our calculations, we propose some empirical inequalities for quantifying the effectiveness of such minigaps in making the device unipolar and thus high gain.
Graphene-HgCdTe heterostructure based mid wave IR (MWIR) detectors are being designed for NASA Earth Science applications. Combining Density Functional Theory (DFT) based calculations of the bandstructure with carrier generation and transport model of this detector, we study the essential physics of this novel detector design and project its performance. Combining the best of both these materials can yield high performance and superior detection capabilities.
Proc. SPIE. 11386, Advanced Photon Counting Techniques XIV
KEYWORDS: Systems modeling, Avalanche photodetectors, Avalanche photodiodes, Telecommunications, Monte Carlo methods, Instrument modeling, Internet, Photonic devices, Electronic components, Sensing systems
Some III-V digital alloy avalanche photodiodes demonstrate very low excess noise making them suitable for single photon detection applications. This behavior is attributed to the presence of minigaps in the valence band and high hole effective mass which reduce hole impact ionization. In this work, we present a physics based SPICE compatible compact model for these low noise avalanche photodiodes built from parameters extracted from Environment-Dependent Tight Binding model, that is calibrated to ab-initio Density Functional Theory, and Monte Carlo methods. Using this approach, we can accurately capture the physical characteristics of APDs in integrated photonics circuit simulation.