A Multiscale Materials-to-Systems Modeling of Polycrystalline Pb-Salt Photodetectors

TL;DR

This paper develops a comprehensive multiscale model linking material properties of polycrystalline PbSe photodetectors to their circuit-level performance, enabling simulation and optimization for advanced imaging applications.

Contribution

It introduces a physics-based multiscale modeling framework connecting material characteristics to system-level performance, including a Verilog-A SPICE model for detector simulation.

Findings

Bandstructure explains carrier inversion and long carrier lifetimes.

The 2-current theory captures photoconduction behavior.

Models predict detector responsivity and noise based on material parameters.

Abstract

We present a physics based multiscale materials-to-systems model for polycrystalline $PbSe$ photodetectors that connects fundamental material properties to circuit level performance metrics. From experimentally observed film structures and electrical characterization, we first develop a bandstructure model that explains carrier-type inversion and large carrier lifetimes in sensitized films. The unique bandstructure of the photosensitive film causes separation of generated carriers with holes migrating to the inverted $PbSe|PbI_2$ interface, while electrons are trapped in the bulk of the film inter-grain regions. These flows together forms the 2-current theory of photoconduction that quantitatively captures the $I-V$ relationship in these films. To capture the effect of pixel scaling and minority carrier blocking, we develop a model for the metallic contacts with the detector films based on the relative workfunction differences. We also develop detailed models for various physical parameters such as mobility, lifetime, quantum efficiency, noise etc. that connect the detector performance metrics such as responsivity $\mathcal{R}$ and specific detectivity $\mathcal{D^*}$ intimately with material properties and operating conditions. A compact Verilog-A based SPICE model is developed which can be directly combined with advanced digital ROIC cell designs to simulate and optimize high performance FPAs which form a critical component in the rapidly expanding market of self-driven automotive, IoTs, security, and embedded applications.