Photodetector Behavior Models with Lookup Tables for Variable-Bias Simulation
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Solution Overview
Problem
Current Silicon Photonics (SiPh) process design kits (PDKs) lack user-friendly models for photodetectors (PDs), particularly in simulating their behavior across varying reverse bias voltages and input optical powers, which are noise-sensitive and require wide bias voltage ranges for reliable operation.
Innovation Solution
A built-in lookup-table (LUT) library within the SiPh PDK that stores model parameters for photodetectors, enabling automatic parameter retrieval based on user inputs, including reverse bias voltage, input optical power, and process and temperature conditions, facilitating co-simulation with electronic circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photodetector models are included in SiPh PDKs, then simulation capability is improved, but device complexity increases
Solution Approach 1:
The photodetector model is segmented into multiple independent lookup tables, each storing parameters for specific operating conditions (reverse bias voltage, input optical power, temperature, process corner). This segmentation allows the complex model to be broken down into manageable, condition-specific data structures that can be efficiently queried and combined during simulation.
Solution Approach 2:
Model parameters are pre-calculated and stored in lookup tables during PDK creation, covering a wide range of operating conditions. During simulation, users simply query the pre-computed tables with their specific operating conditions, eliminating the need for real-time complex calculations and reducing simulation complexity.
2Reliability
If wide bias voltage range is used for photodetector operation, then reliability is improved, but model complexity increases
Solution Approach 1:
The wide bias voltage range is segmented into multiple discrete voltage levels, with separate lookup tables created for each voltage condition. This allows the model to handle the wide voltage range systematically by selecting and combining results from appropriate voltage-specific tables, rather than attempting to model the entire range with a single complex equation.
Solution Approach 2:
The model uses parameter changes approach by storing pre-computed results for different reverse bias voltages, input optical powers, temperatures, and process corners in lookup tables. The simulation simply retrieves and combines parameters from these tables based on operating conditions, avoiding complex real-time calculations across wide parameter ranges.
3Ease of operation
If lookup-table library is implemented, then ease of operation is improved, but manufacturing precision requirements increase
Solution Approach 1:
All model parameters are pre-calculated with high precision during PDK creation and stored in lookup tables. This preliminary action ensures that manufacturing precision requirements are met during the PDK development phase, while end-users benefit from simple, accurate parameter retrieval without needing to perform complex measurements or calculations.
Solution Approach 2:
The lookup tables contain pre-extracted model parameters that accurately represent the photodetector behavior under various conditions. These tabulated parameters serve as precise copies of the actual device characteristics, allowing users to obtain accurate simulation results without directly measuring or characterizing physical devices.
Data Source
AI summary
A method for simulating a photodetector behavior includes: receiving an input waveform for an photodetector; receiving an input optical power and a reverse bias voltage for the photodetector; searching for, in a lookup-table library, model parameters for a photodetector behavior model based on the input optical power and the reverse bias voltage; and outputting a second waveform from the photodetector behavior model, where the second waveform is indicative of an electrical response of the photodetector receiving the input waveform.