Transistor Simulation Using Multi-Exponential NQS Modeling
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Solution Overview
Problem
Existing compact models for thin film transistors formed from non-single-crystal semiconductor layers fail to accurately reproduce measured results due to the simplification of the non-quasi static (NQS) effect using a single first-order delay function, which is not suitable for describing the NQS effect in trapped charges.
Innovation Solution
A simulation method that calculates the thermal equilibrium trap charge density and transient trap charge density using a function obtained by superimposing multiple exponential functions with different time constants, allowing for a more accurate representation of the NQS effect in trapped charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple first-order delay function is used to model the NQS effect in trapped charges, then the device complexity is reduced and ease of operation is improved, but the measurement precision and reliability of the simulation results deteriorate
Solution Approach 1:
The trapped charge distribution is segmented into multiple exponential components with different time constants, allowing the model to capture the complex transient behavior of trapped charges more accurately while maintaining computational tractability through modular structure
Solution Approach 2:
The model transitions from a single time constant parameter to multiple time constant parameters, enabling more flexible and accurate representation of the NQS effect in trapped charges without significantly increasing computational burden
2Productivity
If a single exponential function is used to describe the time variance of transient trap charge density, then the calculation process is simplified and processing speed is improved, but the ability to accurately reproduce measured results deteriorates
Solution Approach 1:
The transient trap charge density is segmented into multiple exponential terms, each representing different physical processes or charge trapping mechanisms, allowing accurate reproduction of measured results while maintaining efficient calculation through analytical solutions
Solution Approach 2:
The model uses a composite function combining multiple exponential terms with different time constants, analogous to composite materials, to capture the complex behavior of trapped charges more accurately than a single exponential function while remaining computationally efficient
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed simulation method effectively captures the real NQS effect, leading to improved accuracy in simulating the characteristics of thin film transistors, particularly in reproducing measured results for transient response and DC characteristics.
Implementation Method 1
calculating a thermal equilibrium trap charge density Q′T, based on the Poisson's equation expressing a relationship between an electrostatic potential inside the channel and charges including free carrier charges and trapped charges
Data Source
AI summary
A simulation method includes a process of calculating a transient charge density qT of trapped charges after applying a voltage between a gate electrode and a semiconductor layer of a transistor, the charge density qT being calculated with a time variance of the charge density qT being expressed by a function obtained by superimposing multiple exponential functions having mutually different time constants.