Amorphous Silicon Thin-Film Transistors: Operation, Modelling and Applications

Preface
Acknowledgements
Contents
Abbreviations
Symbols
1 Introduction
	References
2 Hydrogenated Amorphous Silicon Thin-Film Transistors
	2.1 Introduction
	2.2 Amorphous Silicon and a-Si:H TFTs
	2.3 Silicon Nitride
	2.4 Thin-Film Transistor Structures
	2.5 Thin-Film Transistor Materials
	2.6 a-Si:H TFTs Performance Requirements
	2.7 a-Si:H TFT Operation
		2.7.1 Subthreshold or Weak Accumulation Regime
		2.7.2 Above Threshold or High Accumulation Regime
		2.7.3 Transitional Regime
		2.7.4 Crystalline-Like Regime
	References
3 Amorphous Silicon-Based MIS Structure
	3.1 Introduction
	3.2 Density of States in the Amorphous Silicon
	3.3 Band Diagram
	3.4 Charge Densities
		3.4.1 Density of Free Electrons
		3.4.2 Charge Density in the Deep Localized States
		3.4.3 Charge Density in Tail Localized States
	3.5 MIS Structure DC Analysis
		3.5.1 Assumptions and Calculation Principle
		3.5.2 Poisson Equation
		3.5.3 Potential Equilibrium
	3.6 Quantitative Study
		3.6.1 Bulk Charge Density
		3.6.2 Electrostatic Field and Electrostatic Potential
		3.6.3 Induced Charge in the Semiconductor
		3.6.4 Localized Charge
		3.6.5 Free Electron Density
	3.7 Profiles Analysis
		3.7.1 Potential Profile
		3.7.2 Charge Densities Profiles
	3.8 Conclusion
	References
4 Hydrogenated Amorphous Silicon Thin-Film Transistor: A DC Analysis
	4.1 Introduction
	4.2 Model Hypotheses
	4.3 Drain Current
		4.3.1 General Expression
		4.3.2 Potential Equilibrium
	4.4 Weak Accumulation Regime
		4.4.1 Poisson Equation
		4.4.2 Potential Equilibrium
		4.4.3 Conduction Charge
		4.4.4 Drain Current
		4.4.5 Simplified Model
	4.5 Strong Accumulation Regime
		4.5.1 Poisson Equation
		4.5.2 Potential Equilibrium
		4.5.3 Conduction Charge
		4.5.4 Drain Current
		4.5.5 Simplified Model
	4.6 Field Effect Mobility
		4.6.1 Mobility Ratio in Weak Accumulation
		4.6.2 Mobility Ratio in Strong Accumulation
	4.7 Blocking State
	4.8 Model Summary
		4.8.1 Weak Accumulation (Vg < Vt)
		4.8.2 Strong Accumulation (Vg ≥ Vt)
	4.9 Model Parameters
	4.10 Current–Voltage Characteristics
	4.11 Threshold Voltage
	4.12 On-to-Off Current Ratio
	4.13 Field Effect Mobility-to-Band Mobility Ratio
	4.14 Conclusion
	References
5 Interface States in Amorphous Silicon Thin-Film Transistors
	5.1 Introduction
	5.2 Current–Voltage Characteristics
		5.2.1 Lower Threshold Regime
		5.2.2 Upper Threshold Regime
	5.3 Field Effect Mobility
	5.4 Subthreshold Swing
	5.5 Surface States Impact
	5.6 Conclusion
	References
6 Hydrogenated Amorphous Silicon Thin-Film Transistor: A Dynamic Analysis
	6.1 Introduction
	6.2 Some Dynamic Model Aspects
	6.3 Capacitance Model
		6.3.1 Calculation of the Charges in Source and Drain Sides
		6.3.2 Source Side Charge Calculation
		6.3.3 Drain Side Charge Calculation
		6.3.4 Total Charge Calculation
		6.3.5 Intrinsic Gate-to-Source Capacitance Calculation
		6.3.6 Intrinsic Gate-to-Drain Capacitance Calculation
	6.4 Total Capacitances Analysis for Transistor Operational Regimes
		6.4.1 Blocking State
		6.4.2 Below Threshold Regime
		6.4.3 Above Threshold Regime
	6.5 Model Analysis
	6.6 Conclusion
	References
7 Amorphous Silicon Thin-Film Transistors for Digital Circuits
	7.1 Introduction
	7.2 a-Si-based Inverter
	7.3 a-Si-based Logic Gates
	7.4 a-Si:H TFT Model Implementation
	7.5 Design Considerations for a-Si Logic Gates
	7.6 Conclusion
	References
8 Amorphous Silicon Thin-Film Transistors for Charge Pump Circuits
	8.1 Introduction
	8.2 The Dickson Charge Pump: Some Considerations
	8.3 a-Si:H TFT-Based Charge Pump
	8.4 Charge Pump Performance
		8.4.1 Transient Regime
		8.4.2 Steady-State Regime
	8.5 Conclusion
	References