Simulation of CMOS APS Operation and Crosstalk in SPICE With Generalized Devices

We present SPICE simulations of a CMOS APS pixel element consisting of the optical sensor with the sensing circuit. The photodiode is simulated at the physics level by means of the so-called Generalized Devices, without any predefined compact model. Conversely, regular compact models are used for MOSFETs present in the circuit. Modeling with Generalized Devices takes into account in SPICE simulations both the layout and the physics of the photodiode, i.e., drift-diffusion transport, optical generation and recombination of excess carriers, capacitive effects and surface recombination. Moreover, electrical coupling between two adjacent pixels, i.e., the electrical crosstalk, is well predicted by the network of Generalized Devices. This approach is supported by TCAD Sentaurus simulations and opens the way to full SPICE simulation of Active Pixel Sensor from the circuit down to the semiconductor level within the same circuit simulation tool.

Prediction of optically-triggered amplification in phototransistor with SPICE circuit simulators

Chiara Rossi, Jean-Michel Sallese

Modeling of optoelectronic devices involves long and complex numerical simulations, usually performed with TCAD tools. Numerical simulations provide accurate results for a single device but are not feasible when dealing with a full circuit comprising several nodes. To solve this issue, we developed a novel approach to simulate optoelectronic devices in standard SPICE circuit simulators, thus avoiding using TCAD tools. The concept is based on a coarse meshing of the semiconductor whose nodes are interconnected with the so-called Generalized Lumped Devices. The Generalized Lumped Devices are four ports devices: two ports simulate real currents and voltages in the semiconductor while two additional ports simulate excess carrier density and gradient through the definition of equivalent currents and voltages. The model behind the Generalized Devices is physics based and can correctly simulate optical generation of excess carriers, drift-diffusion transport, bulk and surface recombination as well as capacitive effects, without the need to introduce fitting or empirical parameters. Moreover, since all inputs and outputs are electrical quantities, the model is fully SPICE-compatible and can be merged with SPICE netlists of circuits. In this work, we use the Generalized Devices approach to simulate a bipolar phototransistor and prove that we can predict the photocurrent versus the collector voltage, for different illumination intensities. The model accurately takes into account the optically-triggered current amplification in the phototransistor. Sentaurus TCAD numerical simulations are in agreement with the Generalized Devices approach. Finally, since the model is physics based, we could assess the impact of different semiconductor parameters, such as doping concentrations, lifetime, surface recombination velocity, on the output characteristics of the phototransistors, directly with SPICE circuit simulators.

SPIE-INT SOC OPTICAL ENGINEERING2020

Full SPICE Simulation of a CMOS Active Pixel Sensor with Generalized Devices

Chiara Rossi, Jean-Michel Sallese

We present SPICE simulations of a CMOS APS pixel element consisting of the optical sensor and the circuit. The photodiode is simulated at the physics level by means of the so-called generalized devices, without any predefined compact model. Conversely, regular compact models are used for MOSFETs. Modeling with Generalized Devices takes into account in SPICE simulations both the layout and the physics of the photodiode, that is drift-diffusion transport, optical generation and recombination of excess carriers, capacitive effects and surface recombination. This approach is supported by T CAD simulations and opens the way to full SPICE simulation of Active Pixel Sensor down to the semiconductor level.

IEEE2019

Spice-compatible modeling of high injection and propagation of minority carriers in the substrate of Smart Power ICs

Pietro Buccella, Maher Kayal, Jean-Michel Sallese, Camillo Stefanucci

Classical substrate noise analysis considers the silicon resistivity of an integrated circuit only as doping dependent besides neglecting diffusion currents as well. In power circuits minority carriers are injected into the substrate and propagate by drift diffusion. In this case the conductivity of the substrate is spatially modulated and this effect is particularly important in high injection regime. In this work a description of the coupling between majority and minority drift diffusion currents is presented. A distributed model of the substrate is then proposed to take into account the conductivity modulation and its feedback on diffusion processes. The model is expressed in terms of equivalent circuits in order to be fully compatible with circuit simulators. The simulation results are then discussed for diodes and bipolar transistors and compared to the ones obtained from physical device simulations and measurements. (C) 2014 Published by Elsevier Ltd.

Elsevier2015

Prediction of optically-triggered amplification in phototransistor with SPICE circuit simulators

Chiara Rossi, Jean-Michel Sallese

SPIE-INT SOC OPTICAL ENGINEERING2020